“Librerías”

library(tseries)
## Registered S3 method overwritten by 'quantmod':
##   method            from
##   as.zoo.data.frame zoo
library(astsa)
library(forecast)
## 
## Attaching package: 'forecast'
## The following object is masked from 'package:astsa':
## 
##     gas
library(MASS)

—————– Instrucciones Laboratorio —————————–

#Para el presente laboratorio utilizaremos la series mensuales de desempleo y de las ventas de pollo

3. En caso que se determine que la serie tiene raíz unitaria, aplicar y describir el procedimiento

para eliminarla e incudir estacionariedad.

4. En caso de Identificar Estecionalidad en la serie, realizar el procedimiendo de diferenciación

estacional de la serie

4. En caso de haber aplicado el procedimiento anterior realizar la prueba estadística ADF para

determinar si la serie tiene raíz unitária y dar la interpretación de la prueba.

5. Obtener la gráfica de la serie con la que se realizará el pronóstico (serie en niveles

o diferenciada).

6. Obtener el acf y pacf de la serie para pronóstico y dar una intuición de cada una.

7. Buscar un modelo SARIMA(p,d,q)x(P,D,Q)s que mejor ajuste, considerando

la tabla de coeficientes, criterios de información y análisis de residuales.

8. Selección del modelo ajustado y su justificación.

9. Realizar le pronóstico de la serie para 24 días en adelante.

Series.Unemp<-unemp
Series.Chicken<-chicken

1. Obtención y creación de la gráfica de la serie de datos original y una breve explicación de la gráfica.

plot(Series.Unemp, main= "Desempleo", col="blue")

plot(Series.Chicken, main= "Ventas de Pollo", col="red")

La gráfica de desempleo se ve en los primeros años una variación aleatoria, es hasta el año 1955hasta cierto punto estacional, hasta el año 1975 que tiene una alza importante. Las ventas de pollo desde el año 2002 hasta el 2016 van a la alza, ´con un comportamiento aleatorio.

log.Series.Unemp<-log(Series.Unemp)
log.Series.Chicken<-log(Series.Chicken)
plot(log.Series.Unemp, main="Desempleo", col="red")

plot(log.Series.Chicken, main="Ventas de pollo", col="blue")

2. Aplicar la prueba estadística ADF para determinar si la serie raíz unitária y dar la interpretación de la prueba.

adf.test(log.Series.Unemp)
## 
##  Augmented Dickey-Fuller Test
## 
## data:  log.Series.Unemp
## Dickey-Fuller = -3.7221, Lag order = 7, p-value = 0.02315
## alternative hypothesis: stationary
adf.test(log.Series.Chicken)
## 
##  Augmented Dickey-Fuller Test
## 
## data:  log.Series.Chicken
## Dickey-Fuller = -2.7479, Lag order = 5, p-value = 0.2637
## alternative hypothesis: stationary

La serie de unemployment tiene un p-value <.05 por tanto no es estacionaria. La serie de ventas de pollo tiene un p-value>.05, por tanto es estacionaria.

3. En caso que se determine que la serie tiene raíz unitaria, aplicar y describir el procedimiento para eliminarla e incudir estacionariedad.

unemp.return.series<-diff(log.Series.Unemp)
chicken.return.series<-diff(log.Series.Chicken)
  1. En caso de Identificar Estacionalidad en la serie, realizar el procedimiendo de diferenciación estacional de la serie
plot(unemp.return.series)

plot(chicken.return.series)

  1. En caso de haber aplicado el procedimiento anterior realizar la prueba estadística ADF para determinar si la serie tiene raíz unitária y dar la interpretación de la prueba.
adf.test(unemp.return.series)
## Warning in adf.test(unemp.return.series): p-value smaller than printed p-value
## 
##  Augmented Dickey-Fuller Test
## 
## data:  unemp.return.series
## Dickey-Fuller = -6.9076, Lag order = 7, p-value = 0.01
## alternative hypothesis: stationary
adf.test(chicken.return.series)
## Warning in adf.test(chicken.return.series): p-value smaller than printed p-value
## 
##  Augmented Dickey-Fuller Test
## 
## data:  chicken.return.series
## Dickey-Fuller = -5.6403, Lag order = 5, p-value = 0.01
## alternative hypothesis: stationary
  1. Obtener la gráfica de la serie con la que se realizará el pronóstico (serie en niveles o diferenciada).
plot(unemp.return.series)

plot(chicken.return.series)

  1. Obtener el acf y pacf de la serie para pronóstico y dar una intuición de cada una.
acf2(unemp.return.series, max.lag = 20)

##      [,1] [,2]  [,3]  [,4] [,5]  [,6] [,7]  [,8]  [,9] [,10] [,11] [,12] [,13]
## ACF  0.02 -0.1 -0.25 -0.10 0.25 -0.11 0.22 -0.12 -0.27 -0.16  0.00  0.74 -0.03
## PACF 0.02 -0.1 -0.25 -0.11 0.21 -0.21 0.25 -0.09 -0.32 -0.14  0.05  0.63 -0.13
##      [,14] [,15] [,16] [,17] [,18] [,19] [,20]
## ACF  -0.16 -0.28 -0.14  0.19 -0.14  0.22 -0.13
## PACF -0.19 -0.11 -0.15 -0.12 -0.12  0.07 -0.01
acf2(chicken.return.series, max.lag = 20)

##      [,1]  [,2]  [,3]  [,4]  [,5]  [,6]  [,7]  [,8]  [,9] [,10] [,11] [,12]
## ACF  0.72  0.37  0.07 -0.08 -0.17 -0.20 -0.26 -0.22 -0.10  0.09  0.26  0.33
## PACF 0.72 -0.31 -0.13  0.05 -0.12 -0.05 -0.17  0.12  0.07  0.15  0.12 -0.02
##      [,13] [,14] [,15] [,16] [,17] [,18] [,19] [,20]
## ACF   0.19  0.03 -0.07 -0.13 -0.21 -0.27 -0.31 -0.23
## PACF -0.24  0.03  0.04 -0.12 -0.10 -0.01 -0.06  0.06
adf.test(chicken.return.series)
## Warning in adf.test(chicken.return.series): p-value smaller than printed p-value
## 
##  Augmented Dickey-Fuller Test
## 
## data:  chicken.return.series
## Dickey-Fuller = -5.6403, Lag order = 5, p-value = 0.01
## alternative hypothesis: stationary
adf.test(unemp.return.series)
## Warning in adf.test(unemp.return.series): p-value smaller than printed p-value
## 
##  Augmented Dickey-Fuller Test
## 
## data:  unemp.return.series
## Dickey-Fuller = -6.9076, Lag order = 7, p-value = 0.01
## alternative hypothesis: stationary
  1. Buscar un modelo SARIMA(p,d,q)x(P,D,Q)s que mejor ajuste, considerando la tabla de coeficientes, criterios de información y análisis de residuales.
season12.diff.log.chicken<-diff(chicken.return.series, 12)
plot(season12.diff.log.chicken)

season12.diff.log.unemp<-diff(unemp.return.series, 12)
plot(season12.diff.log.unemp)

acf2(season12.diff.log.unemp)

##      [,1] [,2] [,3] [,4] [,5]  [,6]  [,7]  [,8]  [,9] [,10] [,11] [,12] [,13]
## ACF  0.15 0.28 0.18 0.12 0.15  0.05 -0.04  0.00 -0.08 -0.17 -0.03 -0.47 -0.16
## PACF 0.15 0.26 0.12 0.02 0.06 -0.02 -0.13 -0.03 -0.06 -0.16  0.05 -0.41 -0.06
##      [,14] [,15] [,16] [,17] [,18] [,19] [,20] [,21] [,22] [,23] [,24] [,25]
## ACF  -0.16 -0.14 -0.16 -0.13  -0.1  0.02  0.01 -0.02  0.00 -0.02  0.00  0.11
## PACF  0.08  0.04 -0.07  0.01   0.0  0.04  0.08 -0.06 -0.15  0.00 -0.24  0.06
##      [,26] [,27] [,28] [,29] [,30] [,31] [,32] [,33] [,34] [,35] [,36] [,37]
## ACF   0.03  0.06  0.10  0.04  0.06  0.03 -0.08  0.01 -0.01 -0.08 -0.04 -0.10
## PACF  0.04  0.02  0.02 -0.01 -0.04  0.04 -0.07 -0.06 -0.08 -0.09 -0.20  0.02
##      [,38] [,39] [,40] [,41] [,42] [,43] [,44] [,45] [,46] [,47] [,48]
## ACF  -0.02 -0.06 -0.10 -0.10 -0.03 -0.17  0.03 -0.03  0.02  0.07  0.08
## PACF  0.06 -0.05 -0.04 -0.08  0.01 -0.10  0.01 -0.04 -0.01 -0.02 -0.05
acf2(season12.diff.log.chicken)

##      [,1]  [,2]  [,3] [,4] [,5]  [,6]  [,7]  [,8]  [,9] [,10] [,11] [,12] [,13]
## ACF  0.75  0.47  0.23 0.14  0.1  0.06 -0.02 -0.10 -0.15 -0.20 -0.27 -0.39 -0.30
## PACF 0.75 -0.20 -0.10 0.14  0.0 -0.08 -0.09 -0.04 -0.01 -0.15 -0.11 -0.24  0.36
##      [,14] [,15] [,16] [,17] [,18] [,19] [,20] [,21] [,22] [,23] [,24] [,25]
## ACF  -0.13  0.07  0.17  0.15  0.09  0.02  0.00 -0.07 -0.13 -0.21 -0.25 -0.25
## PACF  0.09  0.10 -0.01 -0.05 -0.04 -0.13 -0.07 -0.22 -0.08 -0.16 -0.20  0.17
##      [,26] [,27] [,28] [,29] [,30] [,31] [,32] [,33] [,34] [,35] [,36] [,37]
## ACF  -0.25 -0.30 -0.32 -0.31 -0.28 -0.18 -0.06  0.09  0.18  0.20  0.18  0.17
## PACF -0.03  0.02  0.04 -0.09 -0.16 -0.02  0.08  0.00  0.00 -0.19 -0.07  0.22
##      [,38] [,39] [,40] [,41] [,42] [,43] [,44] [,45] [,46] [,47] [,48]
## ACF   0.16  0.15  0.13  0.09  0.09  0.08  0.04 -0.04 -0.12 -0.10 -0.02
## PACF -0.01 -0.04  0.02 -0.06 -0.03  0.06 -0.02 -0.07  0.02 -0.07 -0.09
adf.test(season12.diff.log.unemp)
## Warning in adf.test(season12.diff.log.unemp): p-value smaller than printed p-
## value
## 
##  Augmented Dickey-Fuller Test
## 
## data:  season12.diff.log.unemp
## Dickey-Fuller = -6.0573, Lag order = 7, p-value = 0.01
## alternative hypothesis: stationary
adf.test(season12.diff.log.chicken)
## Warning in adf.test(season12.diff.log.chicken): p-value smaller than printed p-
## value
## 
##  Augmented Dickey-Fuller Test
## 
## data:  season12.diff.log.chicken
## Dickey-Fuller = -4.2555, Lag order = 5, p-value = 0.01
## alternative hypothesis: stationary
chicken.fti1<-sarima(log(chicken),p=1,d=1,q=1,
                                        P=0,D=1,Q=1,
                                        S=12)
## initial  value -4.228217 
## iter   2 value -4.447270
## iter   3 value -4.866760
## iter   4 value -4.878667
## iter   5 value -4.885094
## iter   6 value -4.889257
## iter   7 value -4.891438
## iter   8 value -4.891934
## iter   9 value -4.892053
## iter  10 value -4.892123
## iter  11 value -4.892129
## iter  12 value -4.892131
## iter  13 value -4.892131
## iter  13 value -4.892131
## iter  13 value -4.892131
## final  value -4.892131 
## converged
## initial  value -4.887102 
## iter   2 value -4.888180
## iter   3 value -4.888690
## iter   4 value -4.888695
## iter   5 value -4.888697
## iter   6 value -4.888698
## iter   7 value -4.888698
## iter   7 value -4.888698
## iter   7 value -4.888698
## final  value -4.888698 
## converged

chicken.fti3<-sarima(log(chicken),p=1,d=1,q=1,
                                        P=1,D=0,Q=1,
                                        S=12)
## initial  value -4.372002 
## iter   2 value -4.440306
## iter   3 value -4.844152
## iter   4 value -4.855042
## iter   5 value -4.866371
## iter   6 value -4.882210
## iter   7 value -4.896644
## iter   8 value -4.911045
## iter   9 value -4.936748
## iter  10 value -4.941209
## iter  11 value -4.949631
## iter  12 value -4.951322
## iter  13 value -4.952933
## iter  14 value -4.953267
## iter  15 value -4.953471
## iter  16 value -4.953560
## iter  17 value -4.953733
## iter  18 value -4.954552
## iter  19 value -4.954745
## iter  20 value -4.954805
## iter  21 value -4.954805
## iter  22 value -4.954805
## iter  22 value -4.954805
## iter  22 value -4.954805
## final  value -4.954805 
## converged
## initial  value -4.872865 
## iter   2 value -4.905968
## iter   3 value -4.907057
## iter   4 value -4.909450
## iter   5 value -4.912831
## iter   6 value -4.914046
## iter   7 value -4.915649
## iter   8 value -4.915887
## iter   9 value -4.915942
## iter  10 value -4.915956
## iter  11 value -4.915985
## iter  12 value -4.916028
## iter  13 value -4.916035
## iter  14 value -4.916049
## iter  15 value -4.916067
## iter  16 value -4.916076
## iter  17 value -4.916099
## iter  18 value -4.916124
## iter  19 value -4.916140
## iter  20 value -4.916144
## iter  21 value -4.916144
## iter  22 value -4.916144
## iter  23 value -4.916145
## iter  24 value -4.916145
## iter  25 value -4.916145
## iter  26 value -4.916146
## iter  27 value -4.916146
## iter  28 value -4.916146
## iter  29 value -4.916147
## iter  30 value -4.916147
## iter  30 value -4.916147
## iter  30 value -4.916147
## final  value -4.916147 
## converged

chicken.fti4<-sarima(log(chicken),p=0,d=1,q=1,
                                        P=0,D=1,Q=1,
                                        S=12)
## initial  value -4.228158 
## iter   2 value -4.621534
## iter   3 value -4.715551
## iter   4 value -4.727036
## iter   5 value -4.733402
## iter   6 value -4.733585
## iter   7 value -4.733628
## iter   8 value -4.733643
## iter   8 value -4.733643
## iter   8 value -4.733643
## final  value -4.733643 
## converged
## initial  value -4.754563 
## iter   2 value -4.763053
## iter   3 value -4.764066
## iter   4 value -4.765008
## iter   5 value -4.765055
## iter   6 value -4.765059
## iter   6 value -4.765059
## final  value -4.765059 
## converged

chicken.fti5<-sarima(log(chicken),p=1,d=0,q=0,
                                        P=1,D=1,Q=0,
                                        S=12)
## initial  value -2.732654 
## iter   2 value -4.270378
## iter   3 value -4.275620
## iter   4 value -4.289136
## iter   5 value -4.306748
## iter   6 value -4.306763
## iter   7 value -4.306780
## iter   8 value -4.306858
## iter   9 value -4.306869
## iter  10 value -4.306898
## iter  11 value -4.306908
## iter  12 value -4.306937
## iter  13 value -4.307002
## iter  14 value -4.307126
## iter  15 value -4.307279
## iter  16 value -4.307298
## iter  17 value -4.307346
## iter  18 value -4.307380
## iter  19 value -4.307381
## iter  20 value -4.307426
## iter  21 value -4.307442
## iter  22 value -4.307447
## iter  22 value -4.307447
## final  value -4.307447 
## converged
## initial  value -4.306470 
## iter   2 value -4.306506
## iter   3 value -4.306587
## iter   4 value -4.306694
## iter   5 value -4.306803
## iter   6 value -4.306844
## iter   7 value -4.306855
## iter   8 value -4.306857
## iter   9 value -4.306858
## iter  10 value -4.306868
## iter  11 value -4.306878
## iter  12 value -4.306892
## iter  13 value -4.306897
## iter  14 value -4.306899
## iter  15 value -4.306899
## iter  16 value -4.306900
## iter  17 value -4.306901
## iter  18 value -4.306902
## iter  19 value -4.306903
## iter  20 value -4.306903
## iter  20 value -4.306903
## iter  20 value -4.306903
## final  value -4.306903 
## converged

unemp.fti1<-sarima(log(unemp),p=1,d=1,q=1,
                                        P=0,D=1,Q=1,
                                        S=12)
## initial  value -2.551638 
## iter   2 value -2.702571
## iter   3 value -2.737835
## iter   4 value -2.756882
## iter   5 value -2.758216
## iter   6 value -2.759291
## iter   7 value -2.759540
## iter   8 value -2.760214
## iter   9 value -2.760500
## iter  10 value -2.760825
## iter  11 value -2.762580
## iter  12 value -2.765570
## iter  13 value -2.768812
## iter  14 value -2.771957
## iter  15 value -2.775130
## iter  16 value -2.775185
## iter  17 value -2.775195
## iter  18 value -2.775206
## iter  19 value -2.775210
## iter  20 value -2.775214
## iter  21 value -2.775214
## iter  21 value -2.775214
## iter  21 value -2.775214
## final  value -2.775214 
## converged
## initial  value -2.787571 
## iter   2 value -2.788447
## iter   3 value -2.788740
## iter   4 value -2.788800
## iter   5 value -2.788829
## iter   6 value -2.788860
## iter   7 value -2.788919
## iter   8 value -2.788948
## iter   9 value -2.788952
## iter  10 value -2.788955
## iter  11 value -2.788955
## iter  12 value -2.788956
## iter  13 value -2.788956
## iter  14 value -2.788956
## iter  15 value -2.788956
## iter  15 value -2.788956
## final  value -2.788956 
## converged

unemp.fti1$ttable
##      Estimate     SE  t.value p.value
## ar1    0.8064 0.0721  11.1775       0
## ma1   -0.6742 0.0847  -7.9579       0
## sma1  -0.7118 0.0436 -16.3365       0
season13.ddiff.log.serieChicken<-diff(chicken.return.series, 13)
plot(season13.ddiff.log.serieChicken)

acf2(season13.ddiff.log.serieChicken)

##      [,1]  [,2]  [,3] [,4]  [,5] [,6]  [,7]  [,8]  [,9] [,10] [,11] [,12] [,13]
## ACF  0.67  0.34  0.11 0.09  0.10 0.11 -0.06 -0.12 -0.12 -0.03 -0.02 -0.08  -0.3
## PACF 0.67 -0.19 -0.05 0.17 -0.02 0.02 -0.27  0.12 -0.02  0.03 -0.06 -0.11  -0.3
##      [,14] [,15] [,16] [,17] [,18] [,19] [,20] [,21] [,22] [,23] [,24] [,25]
## ACF  -0.22 -0.06  0.09  0.08  0.01 -0.13 -0.12  -0.1 -0.05 -0.10 -0.11 -0.19
## PACF  0.35  0.03 -0.06  0.00 -0.05 -0.07 -0.12   0.0  0.00 -0.08  0.08 -0.21
##      [,26] [,27] [,28] [,29] [,30] [,31] [,32] [,33] [,34] [,35] [,36] [,37]
## ACF  -0.19 -0.23 -0.26 -0.32 -0.29 -0.21 -0.05  0.07  0.15  0.13  0.22  0.18
## PACF -0.31  0.05 -0.06 -0.18  0.00  0.08 -0.02  0.03  0.06 -0.01  0.18 -0.07
##      [,38] [,39] [,40] [,41] [,42] [,43] [,44] [,45] [,46] [,47] [,48]
## ACF   0.15  0.10  0.06 -0.01  0.06  0.08  0.06 -0.01 -0.05 -0.03  0.13
## PACF -0.13 -0.14 -0.04 -0.04  0.09 -0.02 -0.04 -0.06  0.05  0.10  0.03
adf.test(season13.ddiff.log.serieChicken)
## 
##  Augmented Dickey-Fuller Test
## 
## data:  season13.ddiff.log.serieChicken
## Dickey-Fuller = -3.9264, Lag order = 5, p-value = 0.01451
## alternative hypothesis: stationary
chicken.fti1<-sarima(log(Series.Chicken),p=1,d=1,q=1,
                     P=1,D=1,Q=1,
                     S=12)
## initial  value -4.215806 
## iter   2 value -4.442822
## iter   3 value -4.796222
## iter   4 value -4.833307
## iter   5 value -4.838954
## iter   6 value -4.847489
## iter   7 value -4.850336
## iter   8 value -4.850991
## iter   9 value -4.851243
## iter  10 value -4.851267
## iter  11 value -4.851274
## iter  12 value -4.851276
## iter  13 value -4.851277
## iter  13 value -4.851277
## iter  13 value -4.851277
## final  value -4.851277 
## converged
## initial  value -4.880157 
## iter   2 value -4.886418
## iter   3 value -4.888499
## iter   4 value -4.888723
## iter   5 value -4.888787
## iter   6 value -4.888800
## iter   7 value -4.888807
## iter   8 value -4.888807
## iter   8 value -4.888807
## iter   8 value -4.888807
## final  value -4.888807 
## converged

chicken.fti2<-sarima(log(Series.Chicken),p=1,d=1,q=1,
                     P=0,D=1,Q=1,
                     S=12)
## initial  value -4.228217 
## iter   2 value -4.447270
## iter   3 value -4.866760
## iter   4 value -4.878667
## iter   5 value -4.885094
## iter   6 value -4.889257
## iter   7 value -4.891438
## iter   8 value -4.891934
## iter   9 value -4.892053
## iter  10 value -4.892123
## iter  11 value -4.892129
## iter  12 value -4.892131
## iter  13 value -4.892131
## iter  13 value -4.892131
## iter  13 value -4.892131
## final  value -4.892131 
## converged
## initial  value -4.887102 
## iter   2 value -4.888180
## iter   3 value -4.888690
## iter   4 value -4.888695
## iter   5 value -4.888697
## iter   6 value -4.888698
## iter   7 value -4.888698
## iter   7 value -4.888698
## iter   7 value -4.888698
## final  value -4.888698 
## converged

8. Selección del modelo ajustado y su justificación.

library("PerformanceAnalytics")
## Loading required package: xts
## Loading required package: zoo
## 
## Attaching package: 'zoo'
## The following objects are masked from 'package:base':
## 
##     as.Date, as.Date.numeric
## 
## Attaching package: 'PerformanceAnalytics'
## The following object is masked from 'package:graphics':
## 
##     legend
chicken.fti2$ttable #pvalues dentro de rango
##      Estimate     SE  t.value p.value
## ar1    0.6332 0.0753   8.4079  0.0000
## ma1    0.2449 0.0852   2.8749  0.0046
## sma1  -0.8241 0.0624 -13.2020  0.0000
chicken.fti1$ttable #pvalues dentro de rango y 
##      Estimate     SE  t.value p.value
## ar1    0.6327 0.0755   8.3844  0.0000
## ma1    0.2455 0.0853   2.8773  0.0045
## sar1  -0.0182 0.0949  -0.1916  0.8483
## sma1  -0.8167 0.0728 -11.2178  0.0000

9. Realizar le pronóstico de la serie para 24 días en adelante.

SARIMA.forcast<-sarima.for(log(Series.Chicken), n.ahead = 24, 1, 1, 1, 0, 1, 1, 12)

SARIMA.forcast$pred
##           Jan      Feb      Mar      Apr      May      Jun      Jul      Aug
## 2016                                                                4.706076
## 2017 4.682485 4.685708 4.692149 4.698681 4.709161 4.718234 4.724330 4.723157
## 2018 4.709516 4.713153 4.719856 4.726554 4.737139 4.746279 4.752416         
##           Sep      Oct      Nov      Dec
## 2016 4.701466 4.690623 4.682630 4.680135
## 2017 4.722610 4.714340 4.707977 4.706513
## 2018
SARIMA.forcast$se
##              Jan         Feb         Mar         Apr         May         Jun
## 2016                                                                        
## 2017 0.044007359 0.049830879 0.055216309 0.060223945 0.064906774 0.069309834
## 2018 0.099682918 0.103708200 0.107602573 0.111372774 0.115026663 0.118572233
##              Jul         Aug         Sep         Oct         Nov         Dec
## 2016             0.007216761 0.015354066 0.023329223 0.030796920 0.037681753
## 2017 0.073470762 0.077833169 0.082329700 0.086820721 0.091230691 0.095522932
## 2018 0.122017091
SARIMA.forcast<-sarima.for(log(Series.Unemp), n.ahead = 24, 1, 1, 1, 0, 1, 1, 12)

SARIMA.forcast$pred
##           Jan      Feb      Mar      Apr      May      Jun      Jul      Aug
## 1979 6.515336 6.523716 6.474964 6.366666 6.310446 6.502138 6.474210 6.414748
## 1980 6.532327 6.539105 6.489061 6.379721 6.322661 6.513675 6.485200 6.425297
##           Sep      Oct      Nov      Dec
## 1979 6.390059 6.346154 6.379343 6.368991
## 1980 6.400253 6.356062 6.389019 6.378481
SARIMA.forcast$se
##             Jan        Feb        Mar        Apr        May        Jun
## 1979 0.06076454 0.09179104 0.11871120 0.14343310 0.16658312 0.18845187
## 1980 0.32167678 0.34318048 0.36419653 0.38467213 0.40458407 0.42392859
##             Jul        Aug        Sep        Oct        Nov        Dec
## 1979 0.20920972 0.22897545 0.24784207 0.26588779 0.28318099 0.29978269
## 1980 0.44271447 0.46095838 0.47868164 0.49590810 0.51266271 0.52897052