Autoregressive Integrated Moving Average Process

Time Series

Description for Autoregressive Integrated Moving Average Process

Yeongeun Jeon , Jung In Seo
2024-01-18

1. 함수 설명

함수 설명
arima() ARIMA모형의 차수 \(p\)\(q\), 차분 수 \(d\)를 지정하여 모형 구축
auto.arima() 모형의 차수 지정없이 자동적으로 최적화된 모형 구축
acf() 상관도표그림
pacf() 부분상관도표그림
Box.test() Ljung-Box Test
checkresiduals() 잔차가 백색잡음과정의 가정을 만족하는지 확인할 때 사용
forecast() 예측

2. Random Walk and Momentum Plot

# AR(1)과정을 따르는 시계열 생성
set.seed(4631)
y1 <- arima.sim(n = 500,                 # 생성하고자하는 시계열 개수
               list(ar = c(0.4)))        # AR(1)과정 : Y_t = 0.4Y_{t-1}
y1
Time Series:
Start = 1 
End = 500 
Frequency = 1 
  [1] -0.912343409 -1.701603284  1.309603454  0.691301009  0.832229499
  [6]  0.555481039 -0.026684342 -0.362545410  0.693315964 -0.075195230
 [11]  0.122254548 -0.370393783 -0.254577654  0.187517312 -1.708057556
 [16]  0.986697733 -0.640294098 -0.885591883 -0.993104578 -0.135172972
 [21] -0.194449428 -0.123467230 -1.216275158 -0.931739467  0.031253153
 [26] -1.499635290  1.319634259  2.398330132 -0.229766437  1.332681837
 [31]  0.157756638 -0.103097574 -0.102247983  2.536262232  3.218027097
 [36]  0.445937187 -0.177490207 -1.602786627 -0.913088486 -1.406607759
 [41]  0.099831368 -1.448052841  0.277834307  0.308540220  0.604106907
 [46]  0.372668105  1.287859364  1.821393863  3.624531543  0.972845982
 [51] -0.896416641 -1.777569846 -0.695491554 -1.375497500  1.007413097
 [56]  1.142459616  0.721150425 -0.400368442 -0.961452076 -0.969140832
 [61] -1.968814756 -0.798978245 -1.022224506 -1.673391629 -0.705015657
 [66]  0.731069223 -0.427970435  1.303036486  1.862548515  0.017150757
 [71]  1.279744874  1.015345454  2.535688480  1.043884770  1.103283049
 [76]  2.050819678  0.166049018  1.325027055  0.982567526 -1.866691371
 [81] -1.395834381 -2.988217256 -0.158685151 -0.491788055 -0.277597713
 [86]  1.604608492  0.982089512  0.125541809  0.635742936 -0.235507928
 [91]  0.132245190 -0.483377174  0.351436414  2.254957441 -0.203113635
 [96]  1.751899755  1.201800038  2.079376478  1.641068416  0.012711375
[101]  0.455767972 -0.247430434 -0.419432042 -1.387682589 -0.806270199
[106] -1.412385197 -1.392636594  1.346065579  0.313476772  0.845857651
[111]  0.029078760  0.054460112 -0.885253382 -0.146332643 -0.618382418
[116] -0.920818943 -0.338097474 -0.752403660 -1.223742893  0.689190649
[121]  0.539929591  1.258735015  0.022750117 -0.869336438 -0.828436846
[126] -2.166858885  0.273965986 -1.037722970 -0.589593679  1.943031697
[131]  0.861840955 -0.520984536  0.770711156  1.101170054  0.846006091
[136] -2.173509959 -1.102412181  0.596310901 -0.281340324  0.879172771
[141] -0.409098649  1.747917946  0.444448222 -0.304067456 -0.970378141
[146] -0.237309951 -0.342986461 -0.497046979 -0.938379568 -0.230699307
[151] -0.696098707 -0.528535492  1.179030894  1.775753907  0.135886565
[156]  0.219726895  1.743976297  3.234301835  0.144757587 -1.026764175
[161] -1.290638719 -0.293860740  0.213341896  0.656327137  0.115984113
[166]  1.718136766  0.476141379 -0.987470475 -1.852852123 -2.641018085
[171] -0.024482023  0.491991907  0.975704783 -0.002667929 -0.136539414
[176] -0.081797455 -0.702349988 -0.149531603  0.467953220  0.075355046
[181] -0.558518159  0.281974471 -0.899797597 -1.328805544 -0.027818037
[186]  0.802736204 -0.968890576 -0.312796925  0.867650846 -0.257391157
[191]  0.172430824 -0.313593354  1.450511226  0.445832929 -0.349042275
[196] -2.148408416 -0.898881311  0.151759003 -2.266476419  0.117458198
[201]  1.766492454 -0.526284231  0.066299695 -0.566873492  0.965266585
[206]  1.037151790 -1.587680491  1.813497932  1.255998632  0.161051227
[211]  3.054247824  0.952734586  0.452260141  0.203109914 -0.612809154
[216] -1.421695279 -0.075559582 -0.150847637 -0.294898135 -0.191676540
[221] -0.984143939 -0.954974484 -1.952447346 -0.407105502 -1.010789331
[226] -0.376014894 -0.639076989 -1.140124930  0.607587073  0.094643343
[231]  1.277664446  1.289747945  0.765406149  0.965295215  0.768660214
[236]  2.119481591  1.975781515  1.218813681  0.168313822  0.299093643
[241]  1.074462951  0.832784873  2.086258930  0.916655229 -0.164630750
[246] -1.621972456 -1.146651373 -1.195654157 -0.949149364  0.278622989
[251] -0.349154803 -0.063271529  0.487016245 -0.256592989 -0.198698480
[256]  0.139972608 -1.401984577 -0.451456758  0.546480685 -0.118633637
[261]  0.834943293  1.232088158 -0.628640225 -1.307409713 -1.459409232
[266] -0.035619335 -0.178265267  0.126249921 -1.136784165 -2.529288363
[271]  0.386093595  0.625958961 -1.444598418 -0.757761283 -0.958362055
[276] -1.367402052  0.002037527  0.624906595 -1.513101287  0.318593880
[281]  0.341663053  0.750263380 -1.475926277 -0.157797771 -0.245202005
[286] -0.537848659  0.110833231 -1.759603329 -0.086328201 -0.127624951
[291] -0.587355815 -2.306925358 -0.187697381 -1.456423114 -0.186679580
[296] -0.190593254  0.446225486 -0.710882725  0.669572420 -1.652750327
[301] -2.254961336 -0.242182465  0.667217541  0.935181469  1.634818270
[306]  0.312140714 -1.067727411  0.416256545  0.597315306 -2.083217594
[311] -0.686914533  1.523376113 -0.589944868  0.809860833 -0.978598351
[316] -2.291625802 -0.468682911 -1.008714414 -1.689834548 -0.417147451
[321] -0.803271601 -0.832076120  0.065363742 -0.093893644 -1.049059664
[326] -1.444510947 -1.076551021  0.159225511  0.899011492  0.495151288
[331] -2.182210398 -0.704122441 -1.850799443 -0.911979956 -0.364270108
[336]  0.833332861  0.886993545  0.118737971 -0.608727843 -1.085932642
[341]  0.539806089  1.230683997  1.145261304  0.979793271  0.981000516
[346]  0.858859490  0.425712618  1.451944450  1.040442611  1.270852691
[351]  0.001724409  0.104234966 -0.341138452 -1.138528598 -1.618354797
[356] -1.699497595 -0.243076411 -0.651603385  1.343148562 -1.751853045
[361] -2.139267445 -1.229228556  0.255161099  1.813250189  1.862858137
[366]  0.208573786  0.501641144 -1.252334702 -1.172962682 -1.129589843
[371] -0.067739846 -0.062815505 -1.508314314 -0.335414905 -0.353518485
[376]  0.208172483  0.262092705  0.531750971 -0.824122936  0.017032118
[381] -1.015173764  0.365974862 -1.400376808 -1.443808435 -0.451407292
[386]  0.066326783 -0.895822894  0.900912062 -0.037442219 -0.456481687
[391]  2.377575658  2.430206896 -1.619430146  0.987079742  0.281160126
[396] -1.018931312 -0.794530108  1.494620796  1.388568007 -0.936099757
[401] -1.617907620 -1.593275135 -0.836974326 -0.798359722 -1.113207216
[406]  0.511917371 -1.735132035  0.177605755 -1.184768329  0.188680990
[411] -0.878350456 -0.586789699 -0.784074820  0.617449054  2.593695064
[416]  0.547644160 -1.303269875  0.256800524 -0.885652387 -0.367378463
[421] -0.458222229  0.632855057 -2.123028093 -0.601463044 -1.402681000
[426] -1.015006105  0.672074035  0.441082153  0.108044662  1.241146031
[431]  0.182850562  0.532864396  2.021748358  1.453454116 -0.351721426
[436] -0.760864939 -0.342109875  0.709747073  0.678984727 -0.345892776
[441]  1.049415015  1.099538689  0.931988534 -0.307293897  0.324674165
[446]  1.332195826  0.397157781  0.460074576  0.722534790  0.911401034
[451]  1.052024961 -0.770966223 -1.270573476  0.567950193  0.663503429
[456]  1.895802731  0.792548728  0.743382531  0.966190659 -1.038656980
[461] -0.638670844 -0.815864620  0.311205909  0.085439372  1.169179615
[466]  0.045130403  1.334452836  2.056890984  0.061869779  0.993814932
[471] -0.051180302  0.181854157 -0.867732369 -1.729196924 -1.068033410
[476] -1.336379582 -2.486448663 -0.743950909 -0.780466420  0.422205583
[481] -0.603969049 -1.086293175 -2.017387073 -2.463539252 -1.517367558
[486] -1.439320711  0.757130325  1.029261284 -1.059658946 -0.542882678
[491]  0.053945454  0.336157628 -0.645807708  0.372731417  2.163157158
[496]  1.349402356  0.636951690  1.163041710  2.250858491 -0.545616025
y2 <- cumsum(y1)                         # cumsum : 누적합
y3 <- cumsum(y2)

par(mfrow=c(3, 1))                       # 3개의 그래프를 한 화면에 출력
plot(y1, type = "l", 
     ylab = expression(y[1]),
     lwd = 1, main = "(a)")
plot(y2, type = "l",
     xlab = "Time", ylab = expression(y[2]),
     lwd = 1, main = "(b)")
plot(y3, type = "l",
     xlab = "Time", ylab = expression(y[3]),
     lwd = 1, main = "(c)")

Result! (a) 그래프는 평균 0 근처에서 무작위로 변하며, 정상시계열로 보인다.
(b) 그래프는 Random Walk로 보인다. → 1차 차분 필요
(c) 그래프는 Momentum (위 또는 아래로 움직이기 시작하면 그 방향으로 계속 움직이는 경향)으로 보인다. → 2차 차분 필요


3. CPI 데이터셋

CSV 파일에 저장되어 있는 CPI (계절 조정된 미국의 소비자 물가 지수) 데이터셋은 1913년 1월 31일부터 2001년 11월 30일까지 월별 CPI가 기록되어져 있다.

# 데이터 불러오기
CPI.dat <- read.csv("C:/Users/User/Desktop/CPI.dat.csv")
CPI.dat
      X.Y..m..d    CPI
1    1913-01-31   9.80
2    1913-02-28   9.80
3    1913-03-31   9.80
4    1913-04-30   9.80
5    1913-05-31   9.70
6    1913-06-30   9.80
7    1913-07-31   9.90
8    1913-08-31   9.90
9    1913-09-30  10.00
10   1913-10-31  10.00
11   1913-11-30  10.10
12   1913-12-31  10.00
13   1914-01-31  10.00
14   1914-02-28   9.90
15   1914-03-31   9.90
16   1914-04-30   9.80
17   1914-05-31   9.90
18   1914-06-30   9.90
19   1914-07-31  10.00
20   1914-08-31  10.20
21   1914-09-30  10.20
22   1914-10-31  10.10
23   1914-11-30  10.20
24   1914-12-31  10.10
25   1915-01-31  10.10
26   1915-02-28  10.00
27   1915-03-31   9.90
28   1915-04-30  10.00
29   1915-05-31  10.10
30   1915-06-30  10.10
31   1915-07-31  10.10
32   1915-08-31  10.10
33   1915-09-30  10.10
34   1915-10-31  10.20
35   1915-11-30  10.30
36   1915-12-31  10.30
37   1916-01-31  10.40
38   1916-02-29  10.40
39   1916-03-31  10.50
40   1916-04-30  10.60
41   1916-05-31  10.70
42   1916-06-30  10.80
43   1916-07-31  10.80
44   1916-08-31  10.90
45   1916-09-30  11.10
46   1916-10-31  11.30
47   1916-11-30  11.50
48   1916-12-31  11.60
49   1917-01-31  11.70
50   1917-02-28  12.00
51   1917-03-31  12.00
52   1917-04-30  12.60
53   1917-05-31  12.80
54   1917-06-30  13.00
55   1917-07-31  12.80
56   1917-08-31  13.00
57   1917-09-30  13.30
58   1917-10-31  13.50
59   1917-11-30  13.50
60   1917-12-31  13.70
61   1918-01-31  14.00
62   1918-02-28  14.10
63   1918-03-31  14.00
64   1918-04-30  14.20
65   1918-05-31  14.50
66   1918-06-30  14.70
67   1918-07-31  15.10
68   1918-08-31  15.40
69   1918-09-30  15.70
70   1918-10-31  16.00
71   1918-11-30  16.30
72   1918-12-31  16.50
73   1919-01-31  16.50
74   1919-02-28  16.20
75   1919-03-31  16.40
76   1919-04-30  16.70
77   1919-05-31  16.90
78   1919-06-30  16.90
79   1919-07-31  17.40
80   1919-08-31  17.70
81   1919-09-30  17.80
82   1919-10-31  18.10
83   1919-11-30  18.50
84   1919-12-31  18.90
85   1920-01-31  19.30
86   1920-02-29  19.50
87   1920-03-31  19.70
88   1920-04-30  20.30
89   1920-05-31  20.60
90   1920-06-30  20.90
91   1920-07-31  20.80
92   1920-08-31  20.30
93   1920-09-30  20.00
94   1920-10-31  19.90
95   1920-11-30  19.80
96   1920-12-31  19.40
97   1921-01-31  19.00
98   1921-02-28  18.40
99   1921-03-31  18.30
100  1921-04-30  18.10
101  1921-05-31  17.70
102  1921-06-30  17.60
103  1921-07-31  17.70
104  1921-08-31  17.70
105  1921-09-30  17.50
106  1921-10-31  17.50
107  1921-11-30  17.40
108  1921-12-31  17.30
109  1922-01-31  16.90
110  1922-02-28  16.90
111  1922-03-31  16.70
112  1922-04-30  16.70
113  1922-05-31  16.70
114  1922-06-30  16.70
115  1922-07-31  16.80
116  1922-08-31  16.60
117  1922-09-30  16.60
118  1922-10-31  16.70
119  1922-11-30  16.80
120  1922-12-31  16.90
121  1923-01-31  16.80
122  1923-02-28  16.80
123  1923-03-31  16.80
124  1923-04-30  16.90
125  1923-05-31  16.90
126  1923-06-30  17.00
127  1923-07-31  17.20
128  1923-08-31  17.10
129  1923-09-30  17.20
130  1923-10-31  17.30
131  1923-11-30  17.30
132  1923-12-31  17.30
133  1924-01-31  17.30
134  1924-02-29  17.20
135  1924-03-31  17.10
136  1924-04-30  17.00
137  1924-05-31  17.00
138  1924-06-30  17.00
139  1924-07-31  17.10
140  1924-08-31  17.00
141  1924-09-30  17.10
142  1924-10-31  17.20
143  1924-11-30  17.20
144  1924-12-31  17.30
145  1925-01-31  17.30
146  1925-02-28  17.20
147  1925-03-31  17.30
148  1925-04-30  17.20
149  1925-05-31  17.30
150  1925-06-30  17.50
151  1925-07-31  17.70
152  1925-08-31  17.70
153  1925-09-30  17.70
154  1925-10-31  17.70
155  1925-11-30  18.00
156  1925-12-31  17.90
157  1926-01-31  17.90
158  1926-02-28  17.90
159  1926-03-31  17.80
160  1926-04-30  17.90
161  1926-05-31  17.80
162  1926-06-30  17.70
163  1926-07-31  17.50
164  1926-08-31  17.40
165  1926-09-30  17.50
166  1926-10-31  17.60
167  1926-11-30  17.70
168  1926-12-31  17.70
169  1927-01-31  17.50
170  1927-02-28  17.40
171  1927-03-31  17.30
172  1927-04-30  17.30
173  1927-05-31  17.40
174  1927-06-30  17.60
175  1927-07-31  17.30
176  1927-08-31  17.20
177  1927-09-30  17.30
178  1927-10-31  17.40
179  1927-11-30  17.30
180  1927-12-31  17.30
181  1928-01-31  17.30
182  1928-02-29  17.10
183  1928-03-31  17.10
184  1928-04-30  17.10
185  1928-05-31  17.20
186  1928-06-30  17.10
187  1928-07-31  17.10
188  1928-08-31  17.10
189  1928-09-30  17.30
190  1928-10-31  17.20
191  1928-11-30  17.20
192  1928-12-31  17.10
193  1929-01-31  17.10
194  1929-02-28  17.10
195  1929-03-31  17.00
196  1929-04-30  16.90
197  1929-05-31  17.00
198  1929-06-30  17.10
199  1929-07-31  17.30
200  1929-08-31  17.30
201  1929-09-30  17.30
202  1929-10-31  17.30
203  1929-11-30  17.30
204  1929-12-31  17.20
205  1930-01-31  17.10
206  1930-02-28  17.00
207  1930-03-31  16.90
208  1930-04-30  17.00
209  1930-05-31  16.90
210  1930-06-30  16.80
211  1930-07-31  16.60
212  1930-08-31  16.50
213  1930-09-30  16.60
214  1930-10-31  16.50
215  1930-11-30  16.40
216  1930-12-31  16.10
217  1931-01-31  15.90
218  1931-02-28  15.70
219  1931-03-31  15.60
220  1931-04-30  15.50
221  1931-05-31  15.30
222  1931-06-30  15.10
223  1931-07-31  15.10
224  1931-08-31  15.10
225  1931-09-30  15.00
226  1931-10-31  14.90
227  1931-11-30  14.70
228  1931-12-31  14.60
229  1932-01-31  14.30
230  1932-02-29  14.10
231  1932-03-31  14.00
232  1932-04-30  13.90
233  1932-05-31  13.70
234  1932-06-30  13.60
235  1932-07-31  13.60
236  1932-08-31  13.50
237  1932-09-30  13.40
238  1932-10-31  13.30
239  1932-11-30  13.20
240  1932-12-31  13.10
241  1933-01-31  12.90
242  1933-02-28  12.70
243  1933-03-31  12.60
244  1933-04-30  12.60
245  1933-05-31  12.60
246  1933-06-30  12.70
247  1933-07-31  13.10
248  1933-08-31  13.20
249  1933-09-30  13.20
250  1933-10-31  13.20
251  1933-11-30  13.20
252  1933-12-31  13.20
253  1934-01-31  13.20
254  1934-02-28  13.30
255  1934-03-31  13.30
256  1934-04-30  13.30
257  1934-05-31  13.30
258  1934-06-30  13.40
259  1934-07-31  13.40
260  1934-08-31  13.40
261  1934-09-30  13.60
262  1934-10-31  13.50
263  1934-11-30  13.50
264  1934-12-31  13.40
265  1935-01-31  13.60
266  1935-02-28  13.70
267  1935-03-31  13.70
268  1935-04-30  13.80
269  1935-05-31  13.80
270  1935-06-30  13.70
271  1935-07-31  13.70
272  1935-08-31  13.70
273  1935-09-30  13.70
274  1935-10-31  13.70
275  1935-11-30  13.80
276  1935-12-31  13.80
277  1936-01-31  13.80
278  1936-02-29  13.80
279  1936-03-31  13.70
280  1936-04-30  13.70
281  1936-05-31  13.70
282  1936-06-30  13.80
283  1936-07-31  13.90
284  1936-08-31  14.00
285  1936-09-30  14.00
286  1936-10-31  14.00
287  1936-11-30  14.00
288  1936-12-31  14.00
289  1937-01-31  14.10
290  1937-02-28  14.10
291  1937-03-31  14.20
292  1937-04-30  14.30
293  1937-05-31  14.40
294  1937-06-30  14.40
295  1937-07-31  14.50
296  1937-08-31  14.50
297  1937-09-30  14.60
298  1937-10-31  14.60
299  1937-11-30  14.50
300  1937-12-31  14.40
301  1938-01-31  14.20
302  1938-02-28  14.10
303  1938-03-31  14.10
304  1938-04-30  14.20
305  1938-05-31  14.10
306  1938-06-30  14.10
307  1938-07-31  14.10
308  1938-08-31  14.10
309  1938-09-30  14.10
310  1938-10-31  14.00
311  1938-11-30  14.00
312  1938-12-31  14.00
313  1939-01-31  14.00
314  1939-02-28  13.90
315  1939-03-31  13.90
316  1939-04-30  13.80
317  1939-05-31  13.80
318  1939-06-30  13.80
319  1939-07-31  13.80
320  1939-08-31  13.80
321  1939-09-30  14.10
322  1939-10-31  14.00
323  1939-11-30  14.00
324  1939-12-31  14.00
325  1940-01-31  13.90
326  1940-02-29  14.00
327  1940-03-31  14.00
328  1940-04-30  14.00
329  1940-05-31  14.00
330  1940-06-30  14.10
331  1940-07-31  14.00
332  1940-08-31  14.00
333  1940-09-30  14.00
334  1940-10-31  14.00
335  1940-11-30  14.00
336  1940-12-31  14.10
337  1941-01-31  14.10
338  1941-02-28  14.10
339  1941-03-31  14.20
340  1941-04-30  14.30
341  1941-05-31  14.40
342  1941-06-30  14.70
343  1941-07-31  14.70
344  1941-08-31  14.90
345  1941-09-30  15.10
346  1941-10-31  15.30
347  1941-11-30  15.40
348  1941-12-31  15.50
349  1942-01-31  15.70
350  1942-02-28  15.80
351  1942-03-31  16.00
352  1942-04-30  16.10
353  1942-05-31  16.30
354  1942-06-30  16.30
355  1942-07-31  16.40
356  1942-08-31  16.50
357  1942-09-30  16.50
358  1942-10-31  16.70
359  1942-11-30  16.80
360  1942-12-31  16.90
361  1943-01-31  16.90
362  1943-02-28  16.90
363  1943-03-31  17.20
364  1943-04-30  17.40
365  1943-05-31  17.50
366  1943-06-30  17.50
367  1943-07-31  17.40
368  1943-08-31  17.30
369  1943-09-30  17.40
370  1943-10-31  17.40
371  1943-11-30  17.40
372  1943-12-31  17.40
373  1944-01-31  17.40
374  1944-02-29  17.40
375  1944-03-31  17.40
376  1944-04-30  17.50
377  1944-05-31  17.50
378  1944-06-30  17.60
379  1944-07-31  17.70
380  1944-08-31  17.70
381  1944-09-30  17.70
382  1944-10-31  17.70
383  1944-11-30  17.70
384  1944-12-31  17.80
385  1945-01-31  17.80
386  1945-02-28  17.80
387  1945-03-31  17.80
388  1945-04-30  17.80
389  1945-05-31  17.90
390  1945-06-30  18.10
391  1945-07-31  18.10
392  1945-08-31  18.10
393  1945-09-30  18.10
394  1945-10-31  18.10
395  1945-11-30  18.10
396  1945-12-31  18.20
397  1946-01-31  18.20
398  1946-02-28  18.10
399  1946-03-31  18.30
400  1946-04-30  18.40
401  1946-05-31  18.50
402  1946-06-30  18.70
403  1946-07-31  19.80
404  1946-08-31  20.20
405  1946-09-30  20.40
406  1946-10-31  20.80
407  1946-11-30  21.30
408  1946-12-31  21.50
409  1947-01-31  21.48
410  1947-02-28  21.62
411  1947-03-31  22.00
412  1947-04-30  22.00
413  1947-05-31  21.95
414  1947-06-30  22.08
415  1947-07-31  22.23
416  1947-08-31  22.40
417  1947-09-30  22.84
418  1947-10-31  22.91
419  1947-11-30  23.06
420  1947-12-31  23.41
421  1948-01-31  23.68
422  1948-02-29  23.67
423  1948-03-31  23.50
424  1948-04-30  23.82
425  1948-05-31  24.01
426  1948-06-30  24.15
427  1948-07-31  24.40
428  1948-08-31  24.43
429  1948-09-30  24.36
430  1948-10-31  24.31
431  1948-11-30  24.16
432  1948-12-31  24.05
433  1949-01-31  24.01
434  1949-02-28  23.91
435  1949-03-31  23.91
436  1949-04-30  23.92
437  1949-05-31  23.91
438  1949-06-30  23.92
439  1949-07-31  23.70
440  1949-08-31  23.70
441  1949-09-30  23.75
442  1949-10-31  23.67
443  1949-11-30  23.70
444  1949-12-31  23.61
445  1950-01-31  23.51
446  1950-02-28  23.61
447  1950-03-31  23.64
448  1950-04-30  23.65
449  1950-05-31  23.77
450  1950-06-30  23.88
451  1950-07-31  24.07
452  1950-08-31  24.20
453  1950-09-30  24.34
454  1950-10-31  24.50
455  1950-11-30  24.60
456  1950-12-31  24.98
457  1951-01-31  25.38
458  1951-02-28  25.83
459  1951-03-31  25.88
460  1951-04-30  25.92
461  1951-05-31  25.99
462  1951-06-30  25.93
463  1951-07-31  25.91
464  1951-08-31  25.86
465  1951-09-30  26.03
466  1951-10-31  26.16
467  1951-11-30  26.32
468  1951-12-31  26.47
469  1952-01-31  26.45
470  1952-02-29  26.41
471  1952-03-31  26.39
472  1952-04-30  26.46
473  1952-05-31  26.47
474  1952-06-30  26.53
475  1952-07-31  26.68
476  1952-08-31  26.69
477  1952-09-30  26.63
478  1952-10-31  26.69
479  1952-11-30  26.69
480  1952-12-31  26.71
481  1953-01-31  26.64
482  1953-02-28  26.59
483  1953-03-31  26.63
484  1953-04-30  26.69
485  1953-05-31  26.70
486  1953-06-30  26.77
487  1953-07-31  26.79
488  1953-08-31  26.85
489  1953-09-30  26.89
490  1953-10-31  26.95
491  1953-11-30  26.85
492  1953-12-31  26.87
493  1954-01-31  26.94
494  1954-02-28  26.99
495  1954-03-31  26.93
496  1954-04-30  26.86
497  1954-05-31  26.93
498  1954-06-30  26.94
499  1954-07-31  26.86
500  1954-08-31  26.85
501  1954-09-30  26.81
502  1954-10-31  26.72
503  1954-11-30  26.78
504  1954-12-31  26.77
505  1955-01-31  26.77
506  1955-02-28  26.82
507  1955-03-31  26.79
508  1955-04-30  26.79
509  1955-05-31  26.77
510  1955-06-30  26.71
511  1955-07-31  26.76
512  1955-08-31  26.72
513  1955-09-30  26.85
514  1955-10-31  26.82
515  1955-11-30  26.88
516  1955-12-31  26.87
517  1956-01-31  26.83
518  1956-02-29  26.86
519  1956-03-31  26.89
520  1956-04-30  26.93
521  1956-05-31  27.03
522  1956-06-30  27.15
523  1956-07-31  27.29
524  1956-08-31  27.31
525  1956-09-30  27.35
526  1956-10-31  27.51
527  1956-11-30  27.51
528  1956-12-31  27.63
529  1957-01-31  27.67
530  1957-02-28  27.80
531  1957-03-31  27.86
532  1957-04-30  27.93
533  1957-05-31  28.00
534  1957-06-30  28.11
535  1957-07-31  28.19
536  1957-08-31  28.28
537  1957-09-30  28.32
538  1957-10-31  28.32
539  1957-11-30  28.41
540  1957-12-31  28.47
541  1958-01-31  28.64
542  1958-02-28  28.70
543  1958-03-31  28.87
544  1958-04-30  28.94
545  1958-05-31  28.94
546  1958-06-30  28.91
547  1958-07-31  28.89
548  1958-08-31  28.94
549  1958-09-30  28.91
550  1958-10-31  28.91
551  1958-11-30  28.95
552  1958-12-31  28.97
553  1959-01-31  29.01
554  1959-02-28  29.00
555  1959-03-31  28.97
556  1959-04-30  28.98
557  1959-05-31  29.04
558  1959-06-30  29.11
559  1959-07-31  29.15
560  1959-08-31  29.18
561  1959-09-30  29.25
562  1959-10-31  29.35
563  1959-11-30  29.35
564  1959-12-31  29.41
565  1960-01-31  29.37
566  1960-02-29  29.41
567  1960-03-31  29.41
568  1960-04-30  29.54
569  1960-05-31  29.57
570  1960-06-30  29.61
571  1960-07-31  29.55
572  1960-08-31  29.61
573  1960-09-30  29.61
574  1960-10-31  29.75
575  1960-11-30  29.78
576  1960-12-31  29.81
577  1961-01-31  29.84
578  1961-02-28  29.84
579  1961-03-31  29.84
580  1961-04-30  29.81
581  1961-05-31  29.84
582  1961-06-30  29.84
583  1961-07-31  29.92
584  1961-08-31  29.94
585  1961-09-30  29.98
586  1961-10-31  29.98
587  1961-11-30  29.98
588  1961-12-31  30.01
589  1962-01-31  30.04
590  1962-02-28  30.11
591  1962-03-31  30.17
592  1962-04-30  30.21
593  1962-05-31  30.24
594  1962-06-30  30.21
595  1962-07-31  30.22
596  1962-08-31  30.28
597  1962-09-30  30.42
598  1962-10-31  30.38
599  1962-11-30  30.38
600  1962-12-31  30.38
601  1963-01-31  30.44
602  1963-02-28  30.48
603  1963-03-31  30.51
604  1963-04-30  30.48
605  1963-05-31  30.51
606  1963-06-30  30.61
607  1963-07-31  30.69
608  1963-08-31  30.75
609  1963-09-30  30.72
610  1963-10-31  30.75
611  1963-11-30  30.78
612  1963-12-31  30.88
613  1964-01-31  30.94
614  1964-02-29  30.91
615  1964-03-31  30.94
616  1964-04-30  30.95
617  1964-05-31  30.98
618  1964-06-30  31.01
619  1964-07-31  31.02
620  1964-08-31  31.05
621  1964-09-30  31.08
622  1964-10-31  31.12
623  1964-11-30  31.21
624  1964-12-31  31.25
625  1965-01-31  31.28
626  1965-02-28  31.28
627  1965-03-31  31.31
628  1965-04-30  31.38
629  1965-05-31  31.48
630  1965-06-30  31.61
631  1965-07-31  31.58
632  1965-08-31  31.55
633  1965-09-30  31.62
634  1965-10-31  31.65
635  1965-11-30  31.75
636  1965-12-31  31.85
637  1966-01-31  31.88
638  1966-02-28  32.08
639  1966-03-31  32.18
640  1966-04-30  32.28
641  1966-05-31  32.35
642  1966-06-30  32.38
643  1966-07-31  32.45
644  1966-08-31  32.65
645  1966-09-30  32.75
646  1966-10-31  32.85
647  1966-11-30  32.88
648  1966-12-31  32.92
649  1967-01-31  32.90
650  1967-02-28  33.00
651  1967-03-31  33.00
652  1967-04-30  33.10
653  1967-05-31  33.10
654  1967-06-30  33.30
655  1967-07-31  33.40
656  1967-08-31  33.50
657  1967-09-30  33.60
658  1967-10-31  33.70
659  1967-11-30  33.90
660  1967-12-31  34.00
661  1968-01-31  34.10
662  1968-02-29  34.20
663  1968-03-31  34.30
664  1968-04-30  34.40
665  1968-05-31  34.50
666  1968-06-30  34.70
667  1968-07-31  34.90
668  1968-08-31  35.00
669  1968-09-30  35.10
670  1968-10-31  35.30
671  1968-11-30  35.40
672  1968-12-31  35.60
673  1969-01-31  35.70
674  1969-02-28  35.80
675  1969-03-31  36.10
676  1969-04-30  36.30
677  1969-05-31  36.40
678  1969-06-30  36.60
679  1969-07-31  36.80
680  1969-08-31  36.90
681  1969-09-30  37.10
682  1969-10-31  37.30
683  1969-11-30  37.50
684  1969-12-31  37.70
685  1970-01-31  37.90
686  1970-02-28  38.10
687  1970-03-31  38.30
688  1970-04-30  38.50
689  1970-05-31  38.60
690  1970-06-30  38.80
691  1970-07-31  38.90
692  1970-08-31  39.00
693  1970-09-30  39.20
694  1970-10-31  39.40
695  1970-11-30  39.60
696  1970-12-31  39.80
697  1971-01-31  39.90
698  1971-02-28  39.90
699  1971-03-31  40.00
700  1971-04-30  40.10
701  1971-05-31  40.30
702  1971-06-30  40.50
703  1971-07-31  40.60
704  1971-08-31  40.70
705  1971-09-30  40.80
706  1971-10-31  40.90
707  1971-11-30  41.00
708  1971-12-31  41.10
709  1972-01-31  41.20
710  1972-02-29  41.40
711  1972-03-31  41.40
712  1972-04-30  41.50
713  1972-05-31  41.60
714  1972-06-30  41.70
715  1972-07-31  41.80
716  1972-08-31  41.90
717  1972-09-30  42.10
718  1972-10-31  42.20
719  1972-11-30  42.40
720  1972-12-31  42.50
721  1973-01-31  42.70
722  1973-02-28  43.00
723  1973-03-31  43.40
724  1973-04-30  43.70
725  1973-05-31  43.90
726  1973-06-30  44.20
727  1973-07-31  44.20
728  1973-08-31  45.00
729  1973-09-30  45.20
730  1973-10-31  45.60
731  1973-11-30  45.90
732  1973-12-31  46.30
733  1974-01-31  46.80
734  1974-02-28  47.30
735  1974-03-31  47.80
736  1974-04-30  48.10
737  1974-05-31  48.60
738  1974-06-30  49.00
739  1974-07-31  49.30
740  1974-08-31  49.90
741  1974-09-30  50.60
742  1974-10-31  51.00
743  1974-11-30  51.50
744  1974-12-31  51.90
745  1975-01-31  52.30
746  1975-02-28  52.60
747  1975-03-31  52.80
748  1975-04-30  53.00
749  1975-05-31  53.10
750  1975-06-30  53.50
751  1975-07-31  54.00
752  1975-08-31  54.20
753  1975-09-30  54.60
754  1975-10-31  54.90
755  1975-11-30  55.30
756  1975-12-31  55.60
757  1976-01-31  55.80
758  1976-02-29  55.90
759  1976-03-31  56.00
760  1976-04-30  56.10
761  1976-05-31  56.40
762  1976-06-30  56.70
763  1976-07-31  57.00
764  1976-08-31  57.30
765  1976-09-30  57.60
766  1976-10-31  57.90
767  1976-11-30  58.10
768  1976-12-31  58.40
769  1977-01-31  58.70
770  1977-02-28  59.30
771  1977-03-31  59.60
772  1977-04-30  60.00
773  1977-05-31  60.20
774  1977-06-30  60.50
775  1977-07-31  60.80
776  1977-08-31  61.10
777  1977-09-30  61.30
778  1977-10-31  61.60
779  1977-11-30  62.00
780  1977-12-31  62.30
781  1978-01-31  62.70
782  1978-02-28  63.00
783  1978-03-31  63.40
784  1978-04-30  63.90
785  1978-05-31  64.50
786  1978-06-30  65.00
787  1978-07-31  65.50
788  1978-08-31  65.90
789  1978-09-30  66.50
790  1978-10-31  67.10
791  1978-11-30  67.50
792  1978-12-31  67.90
793  1979-01-31  68.50
794  1979-02-28  69.20
795  1979-03-31  69.90
796  1979-04-30  70.60
797  1979-05-31  71.40
798  1979-06-30  72.20
799  1979-07-31  73.00
800  1979-08-31  73.70
801  1979-09-30  74.40
802  1979-10-31  75.20
803  1979-11-30  76.00
804  1979-12-31  76.90
805  1980-01-31  78.00
806  1980-02-29  79.00
807  1980-03-31  80.10
808  1980-04-30  80.90
809  1980-05-31  81.70
810  1980-06-30  82.50
811  1980-07-31  82.60
812  1980-08-31  83.20
813  1980-09-30  83.90
814  1980-10-31  84.70
815  1980-11-30  85.60
816  1980-12-31  86.40
817  1981-01-31  87.20
818  1981-02-28  88.00
819  1981-03-31  88.60
820  1981-04-30  89.10
821  1981-05-31  89.70
822  1981-06-30  90.50
823  1981-07-31  91.50
824  1981-08-31  92.20
825  1981-09-30  93.10
826  1981-10-31  93.40
827  1981-11-30  93.80
828  1981-12-31  94.10
829  1982-01-31  94.40
830  1982-02-28  94.70
831  1982-03-31  94.70
832  1982-04-30  95.00
833  1982-05-31  95.90
834  1982-06-30  97.00
835  1982-07-31  97.50
836  1982-08-31  97.70
837  1982-09-30  97.70
838  1982-10-31  98.10
839  1982-11-30  98.00
840  1982-12-31  97.70
841  1983-01-31  97.90
842  1983-02-28  98.00
843  1983-03-31  98.10
844  1983-04-30  98.80
845  1983-05-31  99.20
846  1983-06-30  99.40
847  1983-07-31  99.80
848  1983-08-31 100.10
849  1983-09-30 100.40
850  1983-10-31 100.80
851  1983-11-30 101.10
852  1983-12-31 101.40
853  1984-01-31 102.10
854  1984-02-29 102.60
855  1984-03-31 102.90
856  1984-04-30 103.30
857  1984-05-31 103.50
858  1984-06-30 103.70
859  1984-07-31 104.10
860  1984-08-31 104.40
861  1984-09-30 104.70
862  1984-10-31 105.10
863  1984-11-30 105.30
864  1984-12-31 105.50
865  1985-01-31 105.70
866  1985-02-28 106.30
867  1985-03-31 106.80
868  1985-04-30 107.00
869  1985-05-31 107.20
870  1985-06-30 107.50
871  1985-07-31 107.70
872  1985-08-31 107.90
873  1985-09-30 108.10
874  1985-10-31 108.50
875  1985-11-30 109.00
876  1985-12-31 109.50
877  1986-01-31 109.90
878  1986-02-28 109.70
879  1986-03-31 109.10
880  1986-04-30 108.70
881  1986-05-31 109.00
882  1986-06-30 109.40
883  1986-07-31 109.50
884  1986-08-31 109.60
885  1986-09-30 110.00
886  1986-10-31 110.20
887  1986-11-30 110.40
888  1986-12-31 110.80
889  1987-01-31 111.50
890  1987-02-28 111.90
891  1987-03-31 112.30
892  1987-04-30 112.80
893  1987-05-31 113.10
894  1987-06-30 113.60
895  1987-07-31 113.90
896  1987-08-31 114.40
897  1987-09-30 114.80
898  1987-10-31 115.10
899  1987-11-30 115.50
900  1987-12-31 115.70
901  1988-01-31 116.10
902  1988-02-29 116.20
903  1988-03-31 116.60
904  1988-04-30 117.20
905  1988-05-31 117.60
906  1988-06-30 118.10
907  1988-07-31 118.60
908  1988-08-31 119.00
909  1988-09-30 119.60
910  1988-10-31 120.00
911  1988-11-30 120.40
912  1988-12-31 120.80
913  1989-01-31 121.30
914  1989-02-28 121.70
915  1989-03-31 122.30
916  1989-04-30 123.20
917  1989-05-31 123.80
918  1989-06-30 124.10
919  1989-07-31 124.60
920  1989-08-31 124.60
921  1989-09-30 124.90
922  1989-10-31 125.50
923  1989-11-30 125.90
924  1989-12-31 126.40
925  1990-01-31 127.60
926  1990-02-28 128.10
927  1990-03-31 128.60
928  1990-04-30 129.00
929  1990-05-31 129.20
930  1990-06-30 130.00
931  1990-07-31 130.60
932  1990-08-31 131.70
933  1990-09-30 132.60
934  1990-10-31 133.50
935  1990-11-30 133.80
936  1990-12-31 134.30
937  1991-01-31 134.80
938  1991-02-28 134.90
939  1991-03-31 134.90
940  1991-04-30 135.20
941  1991-05-31 135.70
942  1991-06-30 136.10
943  1991-07-31 136.30
944  1991-08-31 136.70
945  1991-09-30 137.10
946  1991-10-31 137.30
947  1991-11-30 137.90
948  1991-12-31 138.30
949  1992-01-31 138.40
950  1992-02-29 138.70
951  1992-03-31 139.20
952  1992-04-30 139.50
953  1992-05-31 139.80
954  1992-06-30 140.20
955  1992-07-31 140.60
956  1992-08-31 140.90
957  1992-09-30 141.20
958  1992-10-31 141.80
959  1992-11-30 142.20
960  1992-12-31 142.40
961  1993-01-31 142.80
962  1993-02-28 143.20
963  1993-03-31 143.40
964  1993-04-30 143.90
965  1993-05-31 144.30
966  1993-06-30 144.40
967  1993-07-31 144.60
968  1993-08-31 144.90
969  1993-09-30 145.10
970  1993-10-31 145.70
971  1993-11-30 146.00
972  1993-12-31 146.40
973  1994-01-31 146.40
974  1994-02-28 146.80
975  1994-03-31 147.20
976  1994-04-30 147.30
977  1994-05-31 147.60
978  1994-06-30 148.00
979  1994-07-31 148.50
980  1994-08-31 149.10
981  1994-09-30 149.40
982  1994-10-31 149.50
983  1994-11-30 149.90
984  1994-12-31 150.20
985  1995-01-31 150.60
986  1995-02-28 151.00
987  1995-03-31 151.30
988  1995-04-30 151.90
989  1995-05-31 152.20
990  1995-06-30 152.50
991  1995-07-31 152.70
992  1995-08-31 153.00
993  1995-09-30 153.20
994  1995-10-31 153.70
995  1995-11-30 153.80
996  1995-12-31 154.10
997  1996-01-31 154.80
998  1996-02-29 155.10
999  1996-03-31 155.60
1000 1996-04-30 156.20
1001 1996-05-31 156.50
1002 1996-06-30 156.80
1003 1996-07-31 157.10
1004 1996-08-31 157.30
1005 1996-09-30 157.80
1006 1996-10-31 158.30
1007 1996-11-30 158.80
1008 1996-12-31 159.20
1009 1997-01-31 159.50
1010 1997-02-28 159.90
1011 1997-03-31 159.90
1012 1997-04-30 160.00
1013 1997-05-31 160.10
1014 1997-06-30 160.30
1015 1997-07-31 160.50
1016 1997-08-31 160.80
1017 1997-09-30 161.30
1018 1997-10-31 161.60
1019 1997-11-30 161.80
1020 1997-12-31 161.90
1021 1998-01-31 162.10
1022 1998-02-28 162.20
1023 1998-03-31 162.20
1024 1998-04-30 162.40
1025 1998-05-31 162.70
1026 1998-06-30 162.90
1027 1998-07-31 163.20
1028 1998-08-31 163.50
1029 1998-09-30 163.50
1030 1998-10-31 163.90
1031 1998-11-30 164.20
1032 1998-12-31 164.50
1033 1999-01-31 164.80
1034 1999-02-28 164.80
1035 1999-03-31 165.00
1036 1999-04-30 166.00
1037 1999-05-31 166.00
1038 1999-06-30 166.10
1039 1999-07-31 166.70
1040 1999-08-31 167.10
1041 1999-09-30 167.80
1042 1999-10-31 168.20
1043 1999-11-30 168.50
1044 1999-12-31 168.90
1045 2000-01-31 169.40
1046 2000-02-29 170.20
1047 2000-03-31 171.20
1048 2000-04-30 171.10
1049 2000-05-31 171.30
1050 2000-06-30 172.20
1051 2000-07-31 172.70
1052 2000-08-31 172.80
1053 2000-09-30 173.60
1054 2000-10-31 173.90
1055 2000-11-30 174.30
1056 2000-12-31 174.60
1057 2001-01-31 175.70
1058 2001-02-28 176.20
1059 2001-03-31 176.30
1060 2001-04-30 176.80
1061 2001-05-31 177.50
1062 2001-06-30 177.90
1063 2001-07-31 177.40
1064 2001-08-31 177.50
1065 2001-09-30 178.20
1066 2001-10-31 177.60
1067 2001-11-30 177.60
# 1977-01-31 ~ 1987-12-31 CPI만 추출
CPI <- as.matrix(CPI.dat$CPI)[769:900,]  
CPI
  [1]  58.7  59.3  59.6  60.0  60.2  60.5  60.8  61.1  61.3  61.6
 [11]  62.0  62.3  62.7  63.0  63.4  63.9  64.5  65.0  65.5  65.9
 [21]  66.5  67.1  67.5  67.9  68.5  69.2  69.9  70.6  71.4  72.2
 [31]  73.0  73.7  74.4  75.2  76.0  76.9  78.0  79.0  80.1  80.9
 [41]  81.7  82.5  82.6  83.2  83.9  84.7  85.6  86.4  87.2  88.0
 [51]  88.6  89.1  89.7  90.5  91.5  92.2  93.1  93.4  93.8  94.1
 [61]  94.4  94.7  94.7  95.0  95.9  97.0  97.5  97.7  97.7  98.1
 [71]  98.0  97.7  97.9  98.0  98.1  98.8  99.2  99.4  99.8 100.1
 [81] 100.4 100.8 101.1 101.4 102.1 102.6 102.9 103.3 103.5 103.7
 [91] 104.1 104.4 104.7 105.1 105.3 105.5 105.7 106.3 106.8 107.0
[101] 107.2 107.5 107.7 107.9 108.1 108.5 109.0 109.5 109.9 109.7
[111] 109.1 108.7 109.0 109.4 109.5 109.6 110.0 110.2 110.4 110.8
[121] 111.5 111.9 112.3 112.8 113.1 113.6 113.9 114.4 114.8 115.1
[131] 115.5 115.7
# log(CPI)를 차분
CPI_diff1 <- as.matrix(diff(log(CPI), 
                            diff = 1))           # 1번 차분
CPI_diff1
                [,1]
  [1,]  0.0101695792
  [2,]  0.0050462681
  [3,]  0.0066889882
  [4,]  0.0033277901
  [5,]  0.0049710127
  [6,]  0.0049464239
  [7,]  0.0049220772
  [8,]  0.0032679768
  [9,]  0.0048820276
 [10,]  0.0064725145
 [11,]  0.0048270407
 [12,]  0.0064000218
 [13,]  0.0047732788
 [14,]  0.0063291351
 [15,]  0.0078554999
 [16,]  0.0093458624
 [17,]  0.0077220461
 [18,]  0.0076628727
 [19,]  0.0060882989
 [20,]  0.0090635062
 [21,]  0.0089820963
 [22,]  0.0059435539
 [23,]  0.0059084367
 [24,]  0.0087977107
 [25,]  0.0101671174
 [26,]  0.0100647866
 [27,]  0.0099644953
 [28,]  0.0112677248
 [29,]  0.0111421766
 [30,]  0.0110193952
 [31,]  0.0095433580
 [32,]  0.0094531426
 [33,]  0.0106952891
 [34,]  0.0105821093
 [35,]  0.0117725362
 [36,]  0.0142029502
 [37,]  0.0127390258
 [38,]  0.0138280016
 [39,]  0.0099379700
 [40,]  0.0098401778
 [41,]  0.0097442915
 [42,]  0.0012113872
 [43,]  0.0072376673
 [44,]  0.0083782656
 [45,]  0.0094899882
 [46,]  0.0105696815
 [47,]  0.0093023927
 [48,]  0.0092166551
 [49,]  0.0091324836
 [50,]  0.0067950431
 [51,]  0.0056274769
 [52,]  0.0067114346
 [53,]  0.0088790816
 [54,]  0.0109891216
 [55,]  0.0076211583
 [56,]  0.0097140537
 [57,]  0.0032171610
 [58,]  0.0042735108
 [59,]  0.0031931906
 [60,]  0.0031830266
 [61,]  0.0031729270
 [62,]  0.0000000000
 [63,]  0.0031628914
 [64,]  0.0094290903
 [65,]  0.0114049966
 [66,]  0.0051413995
 [67,]  0.0020491810
 [68,]  0.0000000000
 [69,]  0.0040858075
 [70,] -0.0010198879
 [71,] -0.0030659196
 [72,]  0.0020449905
 [73,]  0.0010209291
 [74,]  0.0010198879
 [75,]  0.0071102382
 [76,]  0.0040404095
 [77,]  0.0020140994
 [78,]  0.0040160697
 [79,]  0.0030015030
 [80,]  0.0029925209
 [81,]  0.0039761484
 [82,]  0.0029717704
 [83,]  0.0029629651
 [84,]  0.0068796340
 [85,]  0.0048852076
 [86,]  0.0029197101
 [87,]  0.0038797333
 [88,]  0.0019342366
 [89,]  0.0019305025
 [90,]  0.0038498604
 [91,]  0.0028776998
 [92,]  0.0028694424
 [93,]  0.0038131600
 [94,]  0.0019011413
 [95,]  0.0018975338
 [96,]  0.0018939400
 [97,]  0.0056603925
 [98,]  0.0046926412
 [99,]  0.0018709079
[100,]  0.0018674142
[101,]  0.0027945989
[102,]  0.0018587366
[103,]  0.0018552881
[104,]  0.0018518524
[105,]  0.0036934483
[106,]  0.0045977092
[107,]  0.0045766670
[108,]  0.0036463122
[109,] -0.0018214941
[110,] -0.0054844744
[111,] -0.0036730987
[112,]  0.0027560881
[113,]  0.0036630078
[114,]  0.0009136593
[115,]  0.0009128253
[116,]  0.0036429913
[117,]  0.0018165309
[118,]  0.0018132371
[119,]  0.0036166405
[120,]  0.0062978166
[121,]  0.0035810244
[122,]  0.0035682464
[123,]  0.0044424773
[124,]  0.0026560441
[125,]  0.0044111232
[126,]  0.0026373642
[127,]  0.0043802085
[128,]  0.0034904049
[129,]  0.0026098318
[130,]  0.0034692142
[131,]  0.0017301042
CPI_diff2 <- as.matrix(diff(log(CPI), 
                            diff = 2))           # 2번 차분
CPI_diff2
                [,1]
  [1,] -5.123311e-03
  [2,]  1.642720e-03
  [3,] -3.361198e-03
  [4,]  1.643223e-03
  [5,] -2.458879e-05
  [6,] -2.434673e-05
  [7,] -1.654100e-03
  [8,]  1.614051e-03
  [9,]  1.590487e-03
 [10,] -1.645474e-03
 [11,]  1.572981e-03
 [12,] -1.626743e-03
 [13,]  1.555856e-03
 [14,]  1.526365e-03
 [15,]  1.490362e-03
 [16,] -1.623816e-03
 [17,] -5.917335e-05
 [18,] -1.574574e-03
 [19,]  2.975207e-03
 [20,] -8.140984e-05
 [21,] -3.038542e-03
 [22,] -3.511721e-05
 [23,]  2.889274e-03
 [24,]  1.369407e-03
 [25,] -1.023307e-04
 [26,] -1.002914e-04
 [27,]  1.303230e-03
 [28,] -1.255483e-04
 [29,] -1.227813e-04
 [30,] -1.476037e-03
 [31,] -9.021540e-05
 [32,]  1.242146e-03
 [33,] -1.131798e-04
 [34,]  1.190427e-03
 [35,]  2.430414e-03
 [36,] -1.463924e-03
 [37,]  1.088976e-03
 [38,] -3.890032e-03
 [39,] -9.779219e-05
 [40,] -9.588633e-05
 [41,] -8.532904e-03
 [42,]  6.026280e-03
 [43,]  1.140598e-03
 [44,]  1.111723e-03
 [45,]  1.079693e-03
 [46,] -1.267289e-03
 [47,] -8.573756e-05
 [48,] -8.417154e-05
 [49,] -2.337440e-03
 [50,] -1.167566e-03
 [51,]  1.083958e-03
 [52,]  2.167647e-03
 [53,]  2.110040e-03
 [54,] -3.367963e-03
 [55,]  2.092895e-03
 [56,] -6.496893e-03
 [57,]  1.056350e-03
 [58,] -1.080320e-03
 [59,] -1.016402e-05
 [60,] -1.009952e-05
 [61,] -3.172927e-03
 [62,]  3.162891e-03
 [63,]  6.266199e-03
 [64,]  1.975906e-03
 [65,] -6.263597e-03
 [66,] -3.092218e-03
 [67,] -2.049181e-03
 [68,]  4.085808e-03
 [69,] -5.105695e-03
 [70,] -2.046032e-03
 [71,]  5.110910e-03
 [72,] -1.024061e-03
 [73,] -1.041233e-06
 [74,]  6.090350e-03
 [75,] -3.069829e-03
 [76,] -2.026310e-03
 [77,]  2.001970e-03
 [78,] -1.014567e-03
 [79,] -8.982067e-06
 [80,]  9.836274e-04
 [81,] -1.004378e-03
 [82,] -8.805259e-06
 [83,]  3.916669e-03
 [84,] -1.994426e-03
 [85,] -1.965497e-03
 [86,]  9.600232e-04
 [87,] -1.945497e-03
 [88,] -3.734050e-06
 [89,]  1.919358e-03
 [90,] -9.721606e-04
 [91,] -8.257400e-06
 [92,]  9.437176e-04
 [93,] -1.912019e-03
 [94,] -3.607481e-06
 [95,] -3.593816e-06
 [96,]  3.766453e-03
 [97,] -9.677513e-04
 [98,] -2.821733e-03
 [99,] -3.493761e-06
[100,]  9.271848e-04
[101,] -9.358623e-04
[102,] -3.448493e-06
[103,] -3.435721e-06
[104,]  1.841596e-03
[105,]  9.042609e-04
[106,] -2.104222e-05
[107,] -9.303549e-04
[108,] -5.467806e-03
[109,] -3.662980e-03
[110,]  1.811376e-03
[111,]  6.429187e-03
[112,]  9.069197e-04
[113,] -2.749348e-03
[114,] -8.340113e-07
[115,]  2.730166e-03
[116,] -1.826460e-03
[117,] -3.293802e-06
[118,]  1.803403e-03
[119,]  2.681176e-03
[120,] -2.716792e-03
[121,] -1.277799e-05
[122,]  8.742309e-04
[123,] -1.786433e-03
[124,]  1.755079e-03
[125,] -1.773759e-03
[126,]  1.742844e-03
[127,] -8.898036e-04
[128,] -8.805731e-04
[129,]  8.593824e-04
[130,] -1.739110e-03

Caution! 함수 diff()를 이용하여 시계열을 차분할 수 있으며, 옵션 diff에 차분 횟수를 입력하면 된다.


par(mfrow=c(3, 1))                               # 3개의 그래프를 한 화면에 출력
plot(ts(log(CPI),                                # log(CPI)를 ts로 변환       
        start = c(1977, 1),                      # 시계열의 시작 날짜 / c(1977, 1) : 1977년 1월
        frequency = 12),                         # 주기 / 12 : 월별 시계열로 1년에 12번 관측
     xlab = "year", ylab = "log(CPI)",           # 축 이름
     type = "b",                                 # 점과 선을 함께 표시
     main = "(a)")                               # 제목
plot(ts(as.vector(CPI_diff1),                    # log(CPI)를 1번 차분한 시계열을 ts로 변환   
        start = c(1977, 2),                      # 시계열의 시작 날짜 / c(1977, 2) : 1977년 2월
        frequency = 12),                         
     xlab = "year", ylab = expression(paste(Delta," log(CPI)")),
     type = "b",
     main = "(b)")
plot(ts(as.vector(CPI_diff2),                    # log(CPI)를 2번 차분한 시계열을 ts로 변환 
        start = c(1977, 3),                      # 시계열의 시작 날짜 / c(1977, 3) : 1977년 3월
        frequency = 12),  
     xlab ="year", ylab = expression(paste(Delta^2," log(CPI)")), 
     type = "b", 
     main = "(c)")

Caution! 함수 ts()를 이용하여 시계열 객체로 변환할 수 있으며, 옵션 start에는 시계열의 시작 날짜, 옵션 frequency에는 주기를 입력한다.
Result! (a) 그래프를 통해 원 시계열 log(CPI)는 Momentum 현상을 보인다는 것을 알 수 있다.
(b) 그래프를 통해 1번 차분한 log(CPI)는 Momentum 현상은 보이지 않으나, 시간이 흐름에 따라 평균이 변한다는 것을 알 수 있다.
(c) 그래프를 통해 2번 차분한 log(CPI)는 시간이 흐름에 따라 평균이 0에서 변하지 않는다는 것을 알 수 있다.


3-1. ARIMA 모형

# 2번 차분한 log(CPI)에 MA(2) 모형 구축
fit_ma <- arima(CPI_diff2,
                order = c(0, 0, 2))              # (p, d, q)

fit_ma

Call:
arima(x = CPI_diff2, order = c(0, 0, 2))

Coefficients:
          ma1      ma2  intercept
      -0.3433  -0.3694      0e+00
s.e.   0.0831   0.0837      1e-04

sigma^2 estimated as 5.062e-06:  log likelihood = 607.81,  aic = -1207.62

Result! 2번 차분한 log(CPI)에 대해 구축된 MA(2) 모형, 즉, 원 시계열 log(CPI)에 대해 구축된 ARIMA(0,2,2) 모형은 \((1-B)^2Y_t=\epsilon_t-0.3433\epsilon_{t-1}-0.3694\epsilon_{t-2}\)이다.


# 잔차를 이용한 모형 진단
Box.test(fit_ma$resid,                           # 잔차
         lag = 20, 
         type = "Ljung-Box",
         fitdf = 2)                              # 추정된 theta 개수

    Box-Ljung test

data:  fit_ma$resid
X-squared = 26.956, df = 18, p-value = 0.07983

Result! 귀무가설 \(H_0 : \rho(1)=\rho(2)=\cdots=\rho(20)=0\)에 대한 검정 결과에 따르면, \(p\)값이 0.07983이므로 유의수준 0.05에서 \(p\)값이 0.05보다 크기 때문에 귀무가설을 기각하지 못한다. 즉, 잔차에 대해 시차 20까지의 자기상관계수 \(\rho(1), \rho(2), \cdots, \rho(20)\) 중 유의한 자기상관계수가 적어도 1개 존재한다는 증거가 부족하며, 2번 차분한 log(CPI)에 대해 MA(2) 모형을 가정하는 것이 적절하다.


par(mfrow=c(2,2))                                # 1행에 2개의 그래프를 출력 -> 총 2개의 행으로 4개의 그래프가 출력됨
acf(log(CPI),main = "(a) log(CPI)")
acf(CPI_diff1, main = expression(paste("(b) ",Delta," log(CPI)")))
acf(CPI_diff2, main = expression(paste("(c) ",Delta^2," log(CPI)")))
acf(fit_ma$resid, main = "(d) residuals, ARIMA(0,2,2)")

Result! (a) 그래프를 통해 원 시계열 log(CPI)의 자기상관계수 ACF는 천천히 감소하고 있다는 것을 알 수 있으며, 이는 원 시계열이 비정상시계열임을 의미한다.
(c) 그래프를 통해 2번 차분한 log(CPI)의 자기상관계수 ACF는 처음 2개의 시차에서 큰 자기상관을 가지고, 그 이후는 작은 자기상관을 가진다는 것을 알 수 있다.
(d) 그래프를 통해 2번 차분한 log(CPI)에 구축된 MA(2) 모형의 잔차는 자기상관이 존재하지 않다는 것을 알 수 있다. 이는 2번 차분한 log(CPI)에 MA(2) 모형, 즉, 원 시계열 log(CPI)에 ARIMA(0,2,2) 모형을 가정하는 것이 적절하다는 것을 의미한다.


4. Mishkin 데이터셋

Package "Ecdat"에서 제공하는 Mishkin 데이터셋은 1950년 2월부터 1990년 12월 사이에 인플레이션율에 대한 시계열 데이터셋이다.

# 패키지 설치
pacman::p_load("Ecdat")

# 데이터 불러오기
data(Mishkin, package = "Ecdat")
y <- as.vector(Mishkin[,1])             # 월별 인플레이션율 추출
y
  [1] -3.552289  5.247540  1.692860  5.064298  6.719322 11.668920
  [7]  9.912501  8.346786  6.517766  4.865085 16.076321 19.154240
 [13] 14.061910  4.650814  1.546310  4.627010 -1.540355  1.540355
 [19]  0.000000  7.672257  6.102576  6.209472  4.533152  0.000000
 [25] -7.564866  0.000000 19.570490 -1.494151  1.494151  0.000000
 [31] -1.494151  0.000000  1.494151  0.000000 -1.494151 -2.993894
 [37] -6.010291  3.008908  1.501630  2.997634  4.482457  2.979029
 [43]  2.971549  1.483071  2.960655 -4.443726 -1.484906  2.967978
 [49] -1.483071 -1.484906 -2.839906  2.839906  1.484906  0.000000
 [55] -1.484906 -2.839906 -2.982291  2.982291 -2.982291  0.000000
 [61]  0.000000  1.492020  0.000000  0.000000  0.000000  2.978693
 [67] -2.978693  4.330177  0.000000  1.484906 -2.836390  0.000000
 [73]  0.000000  2.836390  1.483071  5.914023  5.751562  8.774637
 [79] -1.457907  1.457907  5.682521  1.449363  2.893485  0.000000
 [85]  2.886525  2.748830  2.873018  2.866156  7.006195  5.678584
 [91]  1.415482  1.413814  0.000000  4.103441  0.000000  7.020216
 [97]  1.399128  6.844860  2.777502  0.000000  1.386248  1.384744
[103]  0.000000  0.000000  1.383148  1.381556 -1.381556  1.381556
[109] -1.381556  0.000000  1.381556  1.254555  5.504627  2.742874
[115] -1.370653  2.739743  3.973921  1.363010 -2.727571  1.364560
[121]  0.000000  6.799529  0.000000  2.586158  0.000000  0.000000
[127]  1.352397  5.394306  1.344819  0.000000  0.000000  1.343314
[133] -1.343314  1.343314  0.000000  1.341812  5.230890 -1.335972
[139]  2.670459  0.000000  0.000000  0.000000  0.000000  2.664529
[145]  2.658626  2.532271  0.000000  0.000000  2.647071  0.000000
[151]  6.592472 -1.315600  0.000000 -1.317044  1.317044  1.315600
[157]  1.194725  0.000000  0.000000  5.242814  3.917133  0.000000
[163]  1.302875  1.183181  0.000000  2.598952  0.000000  0.000000
[169] -1.298772  1.298772  2.593336  0.000000  2.587653  1.291782
[175] -1.291782  2.582175  1.171857  2.574118  1.284992 -1.284992
[181]  0.000000  1.284992  3.846739  2.557659  6.254851  1.270154
[187] -2.541654  2.541654  0.000000  2.536194  3.679570  0.000000
[193]  7.553715  2.393494  4.999561  0.000000  2.491991  2.486741
[199]  7.317456  1.233940  4.811423  0.000000  0.000000  0.000000
[205]  1.227743  2.451723  2.446724  3.549967  3.649961  4.849325
[211]  2.307577  3.617287  3.606416  2.289339  3.588767  4.768305
[217]  3.456034  4.735883  3.539687  4.596686  3.515803  3.399432
[223]  3.495549  3.485477  5.681739  3.458990  2.300467  3.338259
[229]  4.574945  6.726781  5.662605  3.282331  7.861482  3.252032
[235]  4.457231  4.339972  4.424734  5.408054  7.570396  2.182552
[241]  5.439077  3.153226  7.553640  4.197689  3.211568  5.236804
[247]  2.126986  4.242622  6.240278  4.110415  5.237093  2.088382
[253]  5.110830  5.183215  6.096802  5.041712  6.133401  2.962434
[259]  1.016681  1.015820  2.029064  1.013247  3.952596  1.009064
[265]  5.945445  3.007194  2.999539  2.901685  2.984980  2.977574
[271]  2.880218  4.934430  2.950948  3.834231  2.934329  5.758887
[277]  8.630559 11.440700  9.436906  6.536329  7.438794  3.659775
[283] 19.304211  1.838323  7.242186  8.105994  8.051480  9.785962
[289] 15.814170 12.122030  6.883693 12.010690 10.111450  7.566704
[295] 13.394280 12.342670  9.006326  9.680984  7.246837  4.855838
[301]  6.371189  4.738003  4.719480  5.566699  9.340268 12.388900
[307]  4.665991  5.350513  6.864336  6.061113  5.269925  3.040442
[313]  3.720887  3.778037  5.200997  6.673568  7.379198  5.857414
[319]  5.093520  5.072093  5.117023  3.575525  5.014266  6.435108
[325] 12.054450  6.336976  9.123064  6.255971  7.616233  4.105433
[331]  4.782352  2.760079  4.065748  5.420399  4.033883  6.056223
[337]  7.374409  8.668254  9.873637 10.451070 11.012750  5.793180
[343]  5.119508  7.025764  7.623123  6.306279  6.273224  9.946648
[349] 11.106510 10.389710 11.519510 13.766670 11.877010  9.987637
[355]  9.318593 10.410780  9.167216  6.281625  9.620259 14.005740
[361] 14.956960 14.772750  8.707769 10.170030  8.572340  7.396264
[367]  9.999892 11.967070  7.265405  7.174647  7.693233 10.614180
[373] 15.060890  9.936591  6.880011  7.334265  6.843737  9.197388
[379]  8.644333  9.498251  5.220479  4.722268  4.229963  6.531282
[385]  3.765132  1.835451  1.875277  8.318006 11.909480  8.179443
[391]  2.243804  5.880264  5.358331  1.808168  0.903063  2.664138
[397]  0.409372  0.818200  8.558391  6.479959  4.032262  4.820824
[403]  4.002672  5.979086  3.176779  1.981179  1.582568  6.702875
[409]  5.491976  2.736532  5.843219  3.492417  3.868475  3.856044
[415]  4.994358  5.737063  3.048542  0.000000  0.760985  2.279948
[421]  4.924980  5.281344  4.883469  4.490115  3.729027  1.860177
[427]  2.599458  3.703707  3.692311  4.048485  2.935736  3.659655
[433] -3.293165 -5.508809 -2.579503  3.683244  5.869799  0.365932
[439]  2.193139  5.828813  1.089709  1.088720  1.087844  7.226761
[445]  4.308729  5.364409  6.405601  4.251591  4.236581  3.167622
[451]  6.310269  6.277260  3.126359  1.040348  0.000000  3.115431
[457]  3.107574  5.161263  6.164397  4.092111  5.095515  5.073969
[463]  5.052708  8.040197  3.999936  0.998057  1.993322  5.960278
[469]  4.944349  6.888122  7.823956  6.804426  2.904398  2.897386
[475]  1.927679  3.846190  5.746220  2.862824  1.904730 12.307830
[481]  5.638225  6.544558  1.863323  2.789618  6.484031  4.610040
[487] 10.992540  9.988676  7.212614  2.693695  0.000000
# 시계열 그림
plot(y, type = "l")

Result! 시간의 흐름에 따라 평균이 변하므로 원 시계열은 비정상시계열임이 의심된다.


4-1. 단위근 검정

# 패키지 설치
pacman::p_load("tseries")

# Dickey-Fuller test
adf.test(y)

    Augmented Dickey-Fuller Test

data:  y
Dickey-Fuller = -3.8651, Lag order = 7, p-value = 0.01576
alternative hypothesis: stationary
# Phillips-Perron test
pp.test(y)

    Phillips-Perron Unit Root Test

data:  y
Dickey-Fuller Z(alpha) = -248.75, Truncation lag parameter =
5, p-value = 0.01
alternative hypothesis: stationary
# KPSS test
kpss.test(y)

    KPSS Test for Level Stationarity

data:  y
KPSS Level = 2.51, Truncation lag parameter = 5, p-value =
0.01

Caution! 단위근 검정을 수행하기 위해 Package "tseries"에서 제공하는 함수 adf.test(), pp.test(), kpss.test()를 사용한다.
Result! 1. Dickey-Fuller test를 수행했을 때, \(p\)값이 0.01576이므로 유의수준 0.05에서 \(p\)값이 0.05보다 작기 때문에 귀무가설을 기각한다. 즉, 관측된 시계열은 정상성을 만족한다.
2. Phillips-Perron test를 수행했을 때, \(p\)값이 0.01이므로 유의수준 0.05에서 \(p\)값이 0.05보다 작기 때문에 귀무가설을 기각한다. 즉, 관측된 시계열은 정상성을 만족한다.
3. KPSS test를 수행했을 때, \(p\)값이 0.01이므로 유의수준 0.05에서 \(p\)값이 0.05보다 작기 때문에 귀무가설을 기각한다. 즉, 단위근이 존재하므로 관측된 시계열은 비정상성을 가진다.


4-2. ARIMA 모형 구축

# 패키지 설치
pacman::p_load("forecast")

auto.arima(y,
           max.p = 5, max.q = 5, 
           ic = "bic")              # BIC 기준으로 BIC가 가장 작은 모형을 최적 모형으로 선택
Series: y 
ARIMA(1,1,1) 

Coefficients:
         ar1      ma1
      0.2383  -0.8772
s.e.  0.0550   0.0269

sigma^2 = 8.587:  log likelihood = -1221.62
AIC=2449.25   AICc=2449.29   BIC=2461.83
# ARIMA(1,1,1) 모형 구축
fitARIMA111 <- arima(y, c(1, 1, 1))

Result! 함수 auto.arima()를 이용하여 BIC 기준으로 최적의 모형을 판단했을 때, ARIMA(1,1,1) 모형이 선택되었다. 추정된 모수 결과를 이용하면 구축된 ARIMA(1,1,1) 모형은 \((1-B)Y_t = 0.2383Y_{t-1}+\epsilon_t -0.8772\epsilon_{t-1}\)이다.


# 잔차를 이용한 모형 진단
par(mfrow=c(1,1))
acf(fitARIMA111$resid)            
Box.test(fitARIMA111$resid,
         lag = 15,
         fitdf = 2)                # 추정한 phi와 theta 개수

    Box-Pierce test

data:  fitARIMA111$resid
X-squared = 14.442, df = 13, p-value = 0.3435

Result! 잔차의 자기상관계수 ACF 그래프를 보면 시차 0을 제외하고 막대의 끝이 파란색 선을 넘어가지 않으므로 다른 시차에서 자기상관계수가 통계적으로 유의하다는 증거가 부족하다.
“Ljung-Box” 검정 결과에 따르면, 귀무가설 \(H_0 : \rho(1)=\rho(2)=\cdots=\rho(15)=0\)에 대해 \(p\)값이 0.3435이므로 유의수준 0.05에서 \(p\)값이 0.05보다 크기 때문에 귀무가설을 기각하지 못한다. 즉, 잔차에 대해 시차 15까지의 자기상관계수 \(\rho(1), \rho(2), \cdots, \rho(15)\) 중 유의한 자기상관계수가 적어도 1개 존재한다는 증거가 부족하며, 해당 시계열에 대해 ARIMA(1,1,1) 모형을 가정하는 것이 적절하다.


4-3. 예측

pred <- forecast(fitARIMA111,
                 h = 100)          # 미래 100시점까지 예측
pred
    Point Forecast       Lo 80     Hi 80     Lo 95     Hi 95
492       3.706101 -0.04167452  7.453876 -2.025627  9.437828
493       4.589298  0.60462429  8.573972 -1.504735 10.683331
494       4.799773  0.73892466  8.860620 -1.410758 11.010303
495       4.849930  0.73788314  8.961978 -1.438903 11.138764
496       4.861884  0.70417897  9.019588 -1.496777 11.220544
497       4.864732  0.66298827  9.066476 -1.561281 11.290745
498       4.865411  0.62034731  9.110475 -1.626854 11.357676
499       4.865573  0.57768877  9.153457 -1.692180 11.423325
500       4.865611  0.53534501  9.195878 -1.756959 11.488182
501       4.865620  0.49338614  9.237855 -1.821135 11.552376
502       4.865623  0.45182011  9.279425 -1.884706 11.615951
503       4.865623  0.41064046  9.320606 -1.947685 11.678931
504       4.865623  0.36983763  9.361409 -2.010088 11.741334
505       4.865623  0.32940172  9.401845 -2.071929 11.803176
506       4.865623  0.28932308  9.441924 -2.133224 11.864471
507       4.865623  0.24959239  9.481654 -2.193987 11.925233
508       4.865623  0.21020076  9.521046 -2.254231 11.985478
509       4.865623  0.17113966  9.560107 -2.313970 12.045217
510       4.865623  0.13240091  9.598846 -2.373216 12.104462
511       4.865623  0.09397664  9.637270 -2.431981 12.163227
512       4.865623  0.05585933  9.675387 -2.490276 12.221523
513       4.865623  0.01804173  9.713205 -2.548113 12.279360
514       4.865623 -0.01948312  9.750730 -2.605502 12.336749
515       4.865623 -0.05672191  9.787969 -2.662454 12.393701
516       4.865623 -0.09368109  9.824928 -2.718978 12.450225
517       4.865623 -0.13036685  9.861614 -2.775084 12.506331
518       4.865623 -0.16678519  9.898032 -2.830781 12.562028
519       4.865623 -0.20294187  9.934189 -2.886078 12.617325
520       4.865623 -0.23884244  9.970089 -2.940983 12.672230
521       4.865623 -0.27449228 10.005739 -2.995505 12.726752
522       4.865623 -0.30989655 10.041143 -3.049651 12.780898
523       4.865623 -0.34506028 10.076307 -3.103430 12.834676
524       4.865623 -0.37998830 10.111235 -3.156847 12.888094
525       4.865623 -0.41468527 10.145932 -3.209912 12.941158
526       4.865623 -0.44915574 10.180402 -3.262630 12.993876
527       4.865623 -0.48340408 10.214651 -3.315008 13.046255
528       4.865623 -0.51743452 10.248681 -3.367053 13.098300
529       4.865623 -0.55125118 10.282498 -3.418771 13.150018
530       4.865623 -0.58485803 10.316105 -3.470169 13.201415
531       4.865623 -0.61825894 10.349506 -3.521251 13.252498
532       4.865623 -0.65145763 10.382704 -3.572024 13.303271
533       4.865623 -0.68445775 10.415704 -3.622493 13.353740
534       4.865623 -0.71726281 10.448509 -3.672664 13.403911
535       4.865623 -0.74987622 10.481123 -3.722542 13.453789
536       4.865623 -0.78230132 10.513548 -3.772132 13.503379
537       4.865623 -0.81454132 10.545788 -3.821439 13.552686
538       4.865623 -0.84659937 10.577846 -3.870467 13.601714
539       4.865623 -0.87847849 10.609725 -3.919222 13.650469
540       4.865623 -0.91018167 10.641428 -3.967708 13.698955
541       4.865623 -0.94171177 10.672958 -4.015929 13.747176
542       4.865623 -0.97307161 10.704318 -4.063890 13.795137
543       4.865623 -1.00426392 10.735511 -4.111595 13.842841
544       4.865623 -1.03529134 10.766538 -4.159047 13.890294
545       4.865623 -1.06615646 10.797403 -4.206251 13.937498
546       4.865623 -1.09686182 10.828108 -4.253211 13.984457
547       4.865623 -1.12740986 10.858657 -4.299930 14.031177
548       4.865623 -1.15780297 10.889050 -4.346412 14.077659
549       4.865623 -1.18804350 10.919290 -4.392661 14.123908
550       4.865623 -1.21813371 10.949380 -4.438680 14.169927
551       4.865623 -1.24807582 10.979322 -4.484473 14.215719
552       4.865623 -1.27787201 11.009119 -4.530042 14.261289
553       4.865623 -1.30752437 11.038771 -4.575391 14.306638
554       4.865623 -1.33703499 11.068282 -4.620524 14.351771
555       4.865623 -1.36640586 11.097653 -4.665443 14.396689
556       4.865623 -1.39563896 11.126886 -4.710151 14.441398
557       4.865623 -1.42473620 11.155983 -4.754651 14.485898
558       4.865623 -1.45369947 11.184946 -4.798947 14.530194
559       4.865623 -1.48253060 11.213777 -4.843040 14.574287
560       4.865623 -1.51123138 11.242478 -4.886934 14.618181
561       4.865623 -1.53980356 11.271050 -4.930632 14.661878
562       4.865623 -1.56824885 11.299496 -4.974135 14.705382
563       4.865623 -1.59656893 11.327816 -5.017447 14.748694
564       4.865623 -1.62476545 11.356012 -5.060570 14.791816
565       4.865623 -1.65283999 11.384087 -5.103506 14.834753
566       4.865623 -1.68079414 11.412041 -5.146258 14.877505
567       4.865623 -1.70862943 11.439876 -5.188829 14.920075
568       4.865623 -1.73634736 11.467594 -5.231220 14.962466
569       4.865623 -1.76394940 11.495196 -5.273433 15.004680
570       4.865623 -1.79143700 11.522684 -5.315472 15.046719
571       4.865623 -1.81881157 11.550058 -5.357338 15.088584
572       4.865623 -1.84607448 11.577321 -5.399033 15.130279
573       4.865623 -1.87322710 11.604474 -5.440559 15.171806
574       4.865623 -1.90027075 11.631517 -5.481919 15.213165
575       4.865623 -1.92720674 11.658453 -5.523114 15.254360
576       4.865623 -1.95403634 11.685283 -5.564146 15.295393
577       4.865623 -1.98076080 11.712007 -5.605018 15.336264
578       4.865623 -2.00738135 11.738628 -5.645730 15.376977
579       4.865623 -2.03389918 11.765146 -5.686286 15.417532
580       4.865623 -2.06031549 11.791562 -5.726686 15.457933
581       4.865623 -2.08663142 11.817878 -5.766933 15.498179
582       4.865623 -2.11284812 11.844095 -5.807028 15.538274
583       4.865623 -2.13896670 11.870213 -5.846973 15.578219
584       4.865623 -2.16498824 11.896235 -5.886769 15.618016
585       4.865623 -2.19091383 11.922160 -5.926419 15.657666
586       4.865623 -2.21674452 11.947991 -5.965924 15.697170
587       4.865623 -2.24248134 11.973728 -6.005285 15.736531
588       4.865623 -2.26812530 11.999372 -6.044504 15.775750
589       4.865623 -2.29367742 12.024924 -6.083582 15.814829
590       4.865623 -2.31913866 12.050385 -6.122522 15.853769
591       4.865623 -2.34450999 12.075757 -6.161324 15.892571
plot(pred)

Caution! 예측은 Package "forecast"에서 제공하는 함수 forecast()를 이용하여 수행할 수 있다.
Result! 원 시계열은 비정상성을 가지기 때문에 예측 구간은 발산한다는 것을 알 수 있다.


# 1번 차분한 시계열에 대한 예측
## 시계열 그림
plot(diff(y), type = "l")

Result! 1번 차분한 시계열은 시간의 흐름에 따라 평균이 변하지 않고 분산도 일정해 보이므로 정상시계열로 보인다.


# 1번 차분한 시계열에 MA(3) 모형 구축
fit_diff <- arima(diff(y),
                  order = c(0, 0, 3))

# 잔차를 이용한 모형 진단
acf(fit_diff$resid)            
Box.test(fit_diff$resid,
         lag = 15,
         fitdf = 3)  

    Box-Pierce test

data:  fit_diff$resid
X-squared = 13.346, df = 12, p-value = 0.3444

Result! 잔차의 자기상관계수 ACF 그래프를 보면 시차 0을 제외하고 막대의 끝이 파란색 선을 넘어가지 않으므로 다른 시차에서 자기상관계수가 통계적으로 유의하다는 증거가 부족하다.
“Ljung-Box” 검정 결과에 따르면, 귀무가설 \(H_0 : \rho(1)=\rho(2)=\cdots=\rho(15)=0\)에 대해 \(p\)값이 0.3444이므로 유의수준 0.05에서 \(p\)값이 0.05보다 크기 때문에 귀무가설을 기각하지 못한다. 즉, 잔차에 대해 시차 15까지의 자기상관계수 \(\rho(1), \rho(2), \cdots, \rho(15)\) 중 유의한 자기상관계수가 적어도 1개 존재한다는 증거가 부족하며, 해당 시계열에 대해 MA(3) 모형을 가정하는 것이 적절하다. 이는 1번 차분한 시계열은 정상시계열임을 의미한다.


# 예측
pred.diff <- forecast(fit_diff,
                      h = 100)          # 미래 100시점까지 예측
pred.diff
    Point Forecast      Lo 80    Hi 80     Lo 95    Hi 95
491   3.4279770957 -0.3093655 7.165320 -2.287795 9.143749
492   0.8929253001 -3.5301468 5.315997 -5.871580 7.657430
493   0.5146289502 -3.9250766 4.954335 -6.275315 7.304573
494  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
495  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
496  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
497  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
498  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
499  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
500  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
501  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
502  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
503  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
504  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
505  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
506  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
507  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
508  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
509  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
510  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
511  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
512  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
513  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
514  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
515  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
516  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
517  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
518  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
519  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
520  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
521  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
522  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
523  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
524  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
525  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
526  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
527  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
528  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
529  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
530  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
531  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
532  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
533  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
534  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
535  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
536  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
537  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
538  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
539  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
540  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
541  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
542  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
543  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
544  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
545  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
546  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
547  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
548  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
549  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
550  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
551  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
552  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
553  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
554  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
555  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
556  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
557  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
558  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
559  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
560  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
561  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
562  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
563  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
564  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
565  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
566  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
567  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
568  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
569  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
570  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
571  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
572  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
573  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
574  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
575  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
576  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
577  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
578  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
579  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
580  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
581  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
582  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
583  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
584  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
585  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
586  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
587  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
588  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
589  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
590  -0.0001564659 -4.4582307 4.457918 -6.818193 6.817880
plot(pred.diff)

Result! 원 시계열을 1번 차분한 시계열은 정상성을 가지기 때문에 예측 구간은 수렴한다는 것을 알 수 있다.

Reuse

Text and figures are licensed under Creative Commons Attribution CC BY 4.0. The figures that have been reused from other sources don't fall under this license and can be recognized by a note in their caption: "Figure from ...".