Dari data yang kalian miliki dan sudah melakukan plot data serta uji stasioneritasnya, selanjutnya adalah a. Transformasi awal dan identifikasi model. (jika data kalian tidak stasioner) b. Estimasi parameter dari model yang memungkinkan.
## Warning: package 'tseries' was built under R version 3.6.3
## Registered S3 method overwritten by 'quantmod':
## method from
## as.zoo.data.frame zoo
## Warning: package 'forecast' was built under R version 3.6.3
Data saya tidak bersifat stasioner maka saya melakukan proses differencing
HB_diff <- diff(HB$Harga.Beras,
differences = 1)
ts.plot(HB_diff,
col = "Green",
xlab = "Time",
ylab = "Differencing",
main = "Time Series Plot (Differencing)")HB_log <- log(HB$Harga.Beras)
AR1 <- arima(HB_log,
order = c(1,2,0),
seasonal = list(order = c(0,0,0),
period = NA),
include.mean = F)
summary(AR1)##
## Call:
## arima(x = HB_log, order = c(1, 2, 0), seasonal = list(order = c(0, 0, 0), period = NA),
## include.mean = F)
##
## Coefficients:
## ar1
## 0.1138
## s.e. 0.2043
##
## sigma^2 estimated as 4.492e-05: log likelihood = 114.76, aic = -225.51
##
## Training set error measures:
## ME RMSE MAE MPE MAPE
## Training set -0.0005328198 0.006890307 0.004987783 -0.005629061 0.05302794
## MASE ACF1
## Training set 1.098 0.1248957
Dari summary(arima) terdapat bahwa nilai koefisien AR1 = 0.1138 dan s.e. = 0.2043 dan sigma^2 = 4.492e-05
MA1 <- arima(HB_log,
order = c(0,2,1),
seasonal = list(order = c(0,0,0),
period = NA),
include.mean = F)
summary(MA1)##
## Call:
## arima(x = HB_log, order = c(0, 2, 1), seasonal = list(order = c(0, 0, 0), period = NA),
## include.mean = F)
##
## Coefficients:
## ma1
## 0.2665
## s.e. 0.2227
##
## sigma^2 estimated as 4.399e-05: log likelihood = 115.06, aic = -226.13
##
## Training set error measures:
## ME RMSE MAE MPE MAPE
## Training set -0.0004844921 0.006826072 0.005032781 -0.005116356 0.053504
## MASE ACF1
## Training set 1.107906 0.02282901
Dari summary(arima) terdapat bahwa nilai koefisien ma1 = 0.2665 dan s.e. = 0.2227 serta sigma^2 = 4.399e-05
ARMA1 <- arima(HB_log,
order = c(1,2,1),
seasonal = list(order = c(0,0,0),
period = NA),
include.mean = F)
summary(ARMA1)##
## Call:
## arima(x = HB_log, order = c(1, 2, 1), seasonal = list(order = c(0, 0, 0), period = NA),
## include.mean = F)
##
## Coefficients:
## ar1 ma1
## 0.5226 -1.0000
## s.e. 0.1681 0.0821
##
## sigma^2 estimated as 3.481e-05: log likelihood = 117.64, aic = -229.29
##
## Training set error measures:
## ME RMSE MAE MPE MAPE
## Training set -0.0005328956 0.006161243 0.004549772 -0.005641721 0.04837094
## MASE ACF1
## Training set 1.001577 0.3426282
Dari summary(arima) terdapat bahwa nilai koefisien AR1 = 0.5226, ma1 = -1 dan s.e.ar = 0.1681, s.e.ma = 0.0821 serta sigma^2 = 3.481e-05
AR2 <- arima(HB_log,
order = c(2,2,0),
seasonal = list(order = c(0,0,0),
period = NA),
include.mean = F)
summary(AR2)##
## Call:
## arima(x = HB_log, order = c(2, 2, 0), seasonal = list(order = c(0, 0, 0), period = NA),
## include.mean = F)
##
## Coefficients:
## ar1 ar2
## 0.0585 -0.4731
## s.e. 0.1910 0.1933
##
## sigma^2 estimated as 3.758e-05: log likelihood = 117.36, aic = -228.73
##
## Training set error measures:
## ME RMSE MAE MPE MAPE
## Training set -0.0006140288 0.006369246 0.004948726 -0.006496628 0.05260887
## MASE ACF1
## Training set 1.089402 0.1158287
Dari summary(arima) terdapat bahwa nilai koefisien AR1 = 0.0585, AR2 = -0.4731 dan s.e.1 = 0.1910, s.e.2 = 0.1933 serta sigma^2 = 3.758e-05
MA2 <- arima(HB_log,
order = c(0,2,2),
seasonal = list(order = c(0,0,0),
period = NA),
include.mean = F)
summary(MA2)##
## Call:
## arima(x = HB_log, order = c(0, 2, 2), seasonal = list(order = c(0, 0, 0), period = NA),
## include.mean = F)
##
## Coefficients:
## ma1 ma2
## -0.3519 -0.6480
## s.e. 0.1474 0.1268
##
## sigma^2 estimated as 2.995e-05: log likelihood = 119.72, aic = -233.44
##
## Training set error measures:
## ME RMSE MAE MPE MAPE
## Training set -0.0001839687 0.005777596 0.004429301 -0.001934603 0.0470879
## MASE ACF1
## Training set 0.9750569 0.2695166
Dari summary(arima) terdapat bahwa nilai koefisien MA1 = -0.3519, MA2 = -0.6480 dan s.e.1 = 0.1474, s.e.2 = 0.1268 serta sigma^2 = 2.995e-05
ARMA2 <- arima(HB_log,
order = c(2,2,2),
seasonal = list(order = c(0,0,0),
period = NA),
include.mean = F)
summary(ARMA2)##
## Call:
## arima(x = HB_log, order = c(2, 2, 2), seasonal = list(order = c(0, 0, 0), period = NA),
## include.mean = F)
##
## Coefficients:
## ar1 ar2 ma1 ma2
## 0.5842 -0.3511 -0.7970 -0.2029
## s.e. 0.5470 0.3635 0.5521 0.5440
##
## sigma^2 estimated as 2.829e-05: log likelihood = 120.48, aic = -230.96
##
## Training set error measures:
## ME RMSE MAE MPE MAPE
## Training set -0.0002308872 0.005641318 0.004467831 -0.002436394 0.0474975
## MASE ACF1
## Training set 0.9835388 0.1267005
Dari summary(arima) didapatkan nilai koefisien AR1 = 0.5842, AR2 = -0.3511, MA1 = -0.7970, MA2 = -0.2029 dan s.e.AR1 = 0.5470, s.e.AR2 = 0.3635, s.e.MA1 = 0.5521, s.e.MA2 = 0.5440 serta sigma^2 = 2.829e-05