Libraries

library(kableExtra)
library(tidyverse)
library(ggplot2)
library(dplyr)
library(corrplot)
library(RColorBrewer)
library(GGally)
library(fpp2)
library(grid)
library(gridExtra)
#library(ggpubr)

Forecasting: Principles & Practice

Section 3.7 - Exercise 1

For the following series, find an appropriate Box-Cox transformation in order to stabilise the variance.

  • usnetelec
  • usgdp
  • mcopper
  • enplanements

DataSet: usnetelec

Description: Annual US net electricity generation (billion kwh) for 1949-2003

# Timeseries plot before Transformation:
plot <- autoplot(usnetelec,ylab="billion kwh",xlab="Year") + ggtitle("Annual US net electricity generation")

lambda <- BoxCox.lambda(usnetelec)
cat('BoxCox Transofrmation Parameter, Lambda:', lambda)
## BoxCox Transofrmation Parameter, Lambda: 0.5167714
# Timeseries plot after applying BoxCox Transformation:
plot_boxcox <- autoplot(BoxCox(usnetelec,lambda),ylab="billion kwh",xlab="Year") + ggtitle("Annual US net electricity generation (w/ BoxCox Transformation)")

grid.arrange(plot,plot_boxcox, ncol=2) 

DataSet: usgdp

Description: Quarterly US GDP. 1947:1 - 2006.1.

# Timeseries plot before Transformation:
plot <- autoplot(usgdp,xlab="Year",ylab="US Dollars") + ggtitle("Quarterly US GDP")

lambda <- BoxCox.lambda(usgdp)
cat('BoxCox Transofrmation Parameter, Lambda:', lambda)
## BoxCox Transofrmation Parameter, Lambda: 0.366352
# Timeseries plot after applying BoxCox Transformation:
plot_boxcox <- autoplot(BoxCox(usgdp,lambda),xlab="Year",ylab="US Dollars") + ggtitle("Quarterly US GDP (w/ BoxCox Transformation)")

grid.arrange(plot,plot_boxcox, ncol=2) 

DataSet: mcopper

Description: Monthly copper prices. Copper, grade A, electrolytic wire bars/cathodes,LME,cash (pounds/ton) Source: UNCTAD

# Timeseries plot before Transformation:
plot <- autoplot(mcopper,ylab="pounds per ton",xlab="Year") + ggtitle("Monthly copper price")

lambda <- BoxCox.lambda(mcopper)
cat('BoxCox Transofrmation Parameter, Lambda:', lambda)
## BoxCox Transofrmation Parameter, Lambda: 0.1919047
# Timeseries plot after applying BoxCox Transformation:
plot_boxcox <- autoplot(BoxCox(mcopper,lambda),ylab="pounds per ton",xlab="Year") + ggtitle("Monthly copper price (w/ BoxCox Transformation)")

grid.arrange(plot,plot_boxcox, ncol=2) 

DataSet: enplanements

Description: “Domestic Revenue Enplanements (millions): 1996-2000. SOURCE: Department of Transportation, Bureau of Transportation Statistics, Air Carrier Traffic Statistic Monthly.

# Timeseries plot before Transformation:
plot <- autoplot(enplanements,ylab="millions",xlab="Year") + ggtitle("US domestic enplanements")

lambda <- BoxCox.lambda(enplanements)
cat('BoxCox Transofrmation Parameter, Lambda:', lambda)
## BoxCox Transofrmation Parameter, Lambda: -0.2269461
# Timeseries plot after applying BoxCox Transformation:
plot_boxcox <- autoplot(BoxCox(enplanements,lambda),ylab="millions",xlab="Year") + ggtitle("US domestic enplanements (w/ BoxCox Transformation)")

grid.arrange(plot,plot_boxcox, ncol=2) 

Section 3.7 - Exercise 2

Q. Why is a Box-Cox transformation unhelpful for the cangas data?

DataSet: cangas

Description: Monthly Canadian gas production, billions of cubic metres, January 1960 - February 2005.

# Timeseries plot before Transformation:
plot <- autoplot(cangas,ylab="billion cubic metres",xlab="Year") + ggtitle("Monthly Canadian gas production")

lambda <- BoxCox.lambda(cangas)
cat('BoxCox Transofrmation Parameter, Lambda:', lambda)
## BoxCox Transofrmation Parameter, Lambda: 0.5767759
# Timeseries plot after applying BoxCox Transformation:
plot_boxcox <- autoplot(BoxCox(cangas,lambda),ylab="billion cubic metres",xlab="Year") + ggtitle("Monthly Canadian gas production (w/ BoxCox Transformation)")

grid.arrange(plot,plot_boxcox, ncol=2) 

Analyzing the original plot for cangas data, below variability in seasonal behavior can be observed -

  • Seasonal variability was smaller for years before 1975
  • Increasing seasonal variability can be observed after 1975, and reached highest around 1985
  • Seasonal variability began to decrease significantly after 1990

Comparing the two plots above for cangas data set, it doesn’t look like BoxCox transformation has helped in making the seasonal variation more uniform across time periods. Hence applying Boxcox transformation is not going to simplify the forecasting model for this data set.

Section 3.7 - Exercise 3

Q. What Box-Cox transformation would you select for your retail data (from Exercise 3 in Section 2.10)?

DataSet: Retail

retaildata <- readxl::read_excel("retail.xlsx", skip=1)

head(retaildata, 20) %>% kable() %>% kable_styling(bootstrap_options = c("striped", "hover", "condensed", "responsive")) %>% scroll_box(width="100%",height="300px")
Series ID A3349335T A3349627V A3349338X A3349398A A3349468W A3349336V A3349337W A3349397X A3349399C A3349874C A3349871W A3349790V A3349556W A3349791W A3349401C A3349873A A3349872X A3349709X A3349792X A3349789K A3349555V A3349565X A3349414R A3349799R A3349642T A3349413L A3349564W A3349416V A3349643V A3349483V A3349722T A3349727C A3349641R A3349639C A3349415T A3349349F A3349563V A3349350R A3349640L A3349566A A3349417W A3349352V A3349882C A3349561R A3349883F A3349721R A3349478A A3349637X A3349479C A3349797K A3349477X A3349719C A3349884J A3349562T A3349348C A3349480L A3349476W A3349881A A3349410F A3349481R A3349718A A3349411J A3349638A A3349654A A3349499L A3349902A A3349432V A3349656F A3349361W A3349501L A3349503T A3349360V A3349903C A3349905J A3349658K A3349575C A3349428C A3349500K A3349577J A3349433W A3349576F A3349574A A3349816F A3349815C A3349744F A3349823C A3349508C A3349742A A3349661X A3349660W A3349909T A3349824F A3349507A A3349580W A3349825J A3349434X A3349822A A3349821X A3349581X A3349908R A3349743C A3349910A A3349435A A3349365F A3349746K A3349370X A3349754K A3349670A A3349764R A3349916R A3349589T A3349590A A3349765T A3349371A A3349588R A3349763L A3349372C A3349442X A3349591C A3349671C A3349669T A3349521W A3349443A A3349835L A3349520V A3349841J A3349925T A3349450X A3349679W A3349527K A3349526J A3349598V A3349766V A3349600V A3349680F A3349378T A3349767W A3349451A A3349924R A3349843L A3349844R A3349376L A3349599W A3349377R A3349779F A3349379V A3349842K A3349532C A3349931L A3349605F A3349688X A3349456L A3349774V A3349848X A3349457R A3349851L A3349604C A3349608L A3349609R A3349773T A3349852R A3349775W A3349776X A3349607K A3349849A A3349850K A3349606J A3349932R A3349862V A3349462J A3349463K A3349334R A3349863W A3349781T A3349861T A3349626T A3349617R A3349546T A3349787F A3349333L A3349860R A3349464L A3349389X A3349461F A3349788J A3349547V A3349388W A3349870V A3349396W
1982-04-01 303.1 41.7 63.9 408.7 65.8 91.8 53.6 211.3 94.0 32.7 126.7 178.3 50.4 22.2 43.0 62.4 178.0 61.8 85.4 147.2 1250.2 257.9 17.3 34.9 310.2 58.2 55.8 59.1 173.1 93.6 26.3 119.9 104.2 42.2 15.6 31.6 34.4 123.7 36.4 48.7 85.1 916.2 139.3 NA NA 161.8 31.8 46.6 13.3 91.6 28.9 13.9 42.8 67.5 18.4 11.1 22.0 25.8 77.3 18.7 26.7 45.4 486.3 83.5 6.0 11.3 100.8 15.2 16.0 8.6 39.7 19.1 6.6 25.7 48.9 8.1 6.1 7.2 12.9 34.2 14.3 15.8 30.1 279.4 96.6 12.3 13.1 122.0 19.2 22.5 8.6 50.4 21.4 7.4 28.8 36.5 9.7 6.5 14.6 11.3 42.1 8.0 10.4 18.4 298.3 26.0 NA NA 28.4 6.1 5.1 2.4 13.6 6.7 1.9 8.7 NA 2.9 1.8 4.0 NA NA 1.9 3.5 5.4 79.9 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 12.7 1.2 1.6 15.5 2.7 4.4 2.6 9.7 3.7 2.2 5.9 10.3 2.3 1.1 2.5 2.2 8.1 4.4 3.2 7.6 57.1 933.4 79.6 149.6 1162.6 200.3 243.4 148.6 592.3 268.5 91.4 359.9 460.1 135.1 64.9 125.6 153.5 479.1 146.3 196.1 342.4 3396.4
1982-05-01 297.8 43.1 64.0 404.9 65.8 102.6 55.4 223.8 105.7 35.6 141.3 202.8 49.9 23.1 45.3 63.1 181.5 60.8 84.8 145.6 1300.0 257.4 18.1 34.6 310.1 62.0 58.4 59.2 179.5 95.3 27.1 122.5 110.2 42.1 15.8 31.5 34.4 123.9 36.2 48.9 85.1 931.2 136.0 NA NA 158.7 32.8 49.6 12.7 95.0 30.6 14.7 45.3 69.7 17.7 11.7 21.9 25.9 77.2 19.5 27.3 46.8 492.8 80.6 5.4 11.1 97.1 17.2 19.0 9.5 45.7 21.6 7.0 28.6 52.2 7.5 6.5 7.5 13.0 34.4 14.2 15.8 30.0 288.0 96.4 11.8 13.4 121.6 21.9 27.8 8.2 57.9 24.1 8.0 32.1 43.7 11.0 7.2 15.2 11.6 45.0 8.0 10.3 18.3 318.5 25.4 NA NA 27.7 6.3 4.7 2.5 13.4 7.4 1.9 9.3 NA 2.9 1.9 4.0 NA NA 2.0 3.5 5.5 78.9 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 12.1 1.4 1.6 15.1 3.0 4.9 3.3 11.1 3.8 2.1 5.9 10.6 2.5 1.0 2.5 2.0 8.0 3.4 3.3 6.7 57.3 920.5 80.8 149.7 1150.9 210.3 268.3 151.0 629.6 289.8 96.8 386.6 502.6 134.9 67.7 128.7 154.8 486.1 145.5 196.6 342.1 3497.9
1982-06-01 298.0 40.3 62.7 401.0 62.3 105.0 48.4 215.7 95.1 32.5 127.6 176.3 48.0 22.8 43.7 59.6 174.1 58.7 80.7 139.4 1234.2 261.2 18.1 34.6 313.9 53.8 53.7 59.8 167.3 85.2 24.3 109.6 96.7 38.5 15.2 29.6 33.5 116.8 35.7 47.1 82.8 887.0 143.5 NA NA 166.6 34.9 51.4 12.9 99.2 30.5 14.5 45.1 60.7 17.7 11.5 22.7 25.9 77.7 18.6 26.2 44.8 494.1 82.3 5.2 11.2 98.7 17.4 18.1 8.4 43.9 18.3 6.0 24.3 48.9 6.7 6.1 7.5 12.5 32.7 13.4 15.3 28.7 277.2 95.6 11.3 13.5 120.4 19.9 26.7 7.9 54.4 21.4 7.0 28.5 38.0 10.7 6.6 14.5 10.9 42.5 7.3 10.4 17.7 301.5 25.3 NA NA 27.7 6.4 5.2 2.1 13.7 6.7 1.8 8.6 NA 2.9 1.9 3.9 NA NA 2.0 3.1 5.1 77.5 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 12.5 1.3 1.7 15.5 2.5 4.8 2.7 9.9 3.2 2.0 5.1 9.9 2.3 1.0 2.5 2.0 7.8 3.6 3.5 7.1 55.3 933.6 77.3 149.0 1160.0 198.7 266.1 142.6 607.4 261.9 88.6 350.5 443.8 128.2 65.5 125.0 148.8 467.5 140.2 188.5 328.7 3357.8
1982-07-01 307.9 40.9 65.6 414.4 68.2 106.0 52.1 226.3 95.3 33.5 128.8 172.6 48.6 23.2 46.5 61.9 180.2 60.3 82.4 142.7 1265.0 266.1 18.9 35.2 320.2 57.9 56.9 59.8 174.5 91.6 25.6 117.2 104.6 38.9 15.2 35.2 33.4 122.7 34.6 47.5 82.1 921.3 150.2 NA NA 172.9 34.6 50.9 13.9 99.4 27.9 15.2 43.1 67.9 18.4 13.1 24.3 28.7 84.4 22.6 25.2 47.8 515.6 88.2 5.6 12.1 105.9 18.7 20.3 10.3 49.3 18.6 6.4 25.0 48.3 7.8 6.6 7.9 13.9 36.2 14.5 17.0 31.4 296.1 103.3 12.1 13.8 129.2 19.3 28.2 8.7 56.2 21.8 7.2 29.0 42.0 9.0 7.0 14.6 11.4 42.0 7.8 10.3 18.1 316.4 27.8 NA NA 30.3 5.9 5.2 2.7 13.7 7.1 1.8 8.9 NA 3.1 1.8 4.4 NA NA 1.9 3.6 5.5 82.7 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 13.2 1.4 1.6 16.1 2.8 5.1 2.4 10.2 3.4 2.1 5.4 8.8 2.6 1.1 2.6 2.0 8.3 4.0 3.5 7.5 56.3 972.6 80.4 153.5 1206.4 208.7 273.5 150.1 632.4 267.2 92.1 359.3 459.1 129.9 68.5 136.6 156.1 491.1 146.5 192.0 338.5 3486.8
1982-08-01 299.2 42.1 62.6 403.8 66.0 96.9 54.2 217.1 82.8 29.4 112.3 169.6 51.3 21.4 44.8 60.7 178.1 56.1 80.7 136.8 1217.6 247.2 19.0 33.8 300.1 59.2 56.7 62.2 178.1 85.2 23.5 108.7 92.5 39.5 14.5 34.7 33.2 122.0 32.5 49.3 81.8 883.2 144.0 NA NA 165.9 32.9 51.6 12.8 97.3 27.4 14.1 41.5 66.5 17.8 13.0 23.6 27.7 82.1 22.6 25.6 48.2 501.4 82.3 5.7 11.7 99.7 18.6 19.6 10.6 48.9 17.1 6.0 23.1 49.4 7.9 6.3 8.3 13.7 36.1 13.6 17.5 31.1 288.4 96.6 12.0 13.3 121.9 19.6 27.4 7.9 55.0 18.7 6.6 25.3 38.5 9.1 6.8 15.3 10.9 42.1 7.6 10.1 17.7 300.5 26.6 NA NA 29.0 5.7 4.8 2.9 13.4 5.8 1.7 7.5 NA 3.1 1.8 4.2 NA NA 1.9 3.6 5.5 78.1 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 12.7 1.6 1.6 15.8 2.8 4.6 2.7 10.1 3.1 2.0 5.0 8.8 2.6 0.9 2.8 2.0 8.4 3.6 3.7 7.3 55.4 923.5 81.6 147.3 1152.5 206.2 262.7 153.7 622.6 241.5 83.7 325.2 438.4 133.0 65.2 134.7 152.8 485.7 138.8 192.7 331.5 3355.9
1982-09-01 305.4 42.0 64.4 411.8 62.3 97.5 53.6 213.4 89.4 32.2 121.6 181.4 49.6 21.8 43.9 61.2 176.5 58.1 82.1 140.2 1244.9 262.4 18.4 35.4 316.2 57.1 58.9 63.6 179.6 89.5 24.3 113.8 98.3 41.7 15.1 34.2 34.5 125.5 33.9 50.7 84.6 917.9 146.9 NA NA 169.5 33.7 49.6 14.5 97.9 29.1 15.5 44.5 73.4 18.8 13.0 21.8 29.0 82.6 23.2 26.7 49.8 517.7 84.2 5.8 12.0 102.0 18.8 19.9 11.5 50.2 18.2 6.4 24.6 48.5 7.8 6.4 7.8 14.1 36.0 13.9 17.8 31.7 293.0 101.4 12.3 13.4 127.1 19.9 27.0 8.7 55.6 19.5 7.4 26.9 40.2 10.0 7.1 15.1 11.7 43.9 8.2 10.3 18.5 312.3 27.1 NA NA 29.6 5.3 4.8 2.6 12.8 5.8 1.7 7.5 NA 3.2 1.8 4.0 NA NA 1.9 3.8 5.7 79.1 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 12.9 1.4 1.8 16.0 2.6 4.3 3.1 10.0 3.4 2.2 5.6 9.2 2.6 1.0 2.8 2.2 8.6 4.2 3.9 8.1 57.5 955.9 81.4 151.8 1189.1 200.9 263.1 157.9 622.0 256.2 90.1 346.3 465.1 135.5 66.8 130.4 157.2 489.9 144.3 197.6 341.9 3454.3
1982-10-01 318.0 46.1 66.0 430.1 66.2 99.3 58.0 223.5 83.3 31.9 115.2 173.9 51.6 21.0 45.6 62.1 180.3 53.9 87.3 141.2 1264.2 285.4 20.9 38.0 344.3 66.9 59.6 64.1 190.5 93.0 25.8 118.7 102.8 46.2 16.3 35.9 36.7 135.2 37.7 54.1 91.7 983.3 143.7 NA NA 166.2 31.7 49.1 13.1 93.8 33.4 15.2 48.6 68.3 20.2 12.0 19.3 27.0 78.5 20.8 28.1 48.8 504.2 88.9 6.6 12.7 108.2 18.7 19.7 10.8 49.3 20.7 7.4 28.1 46.1 7.6 7.4 8.4 15.0 38.4 17.2 20.6 37.8 307.9 107.0 14.2 14.1 135.4 18.0 25.5 10.2 53.6 20.8 8.3 29.1 37.4 7.7 7.5 15.0 12.6 42.8 9.3 11.0 20.3 318.7 27.0 NA NA 29.5 5.5 4.2 2.6 12.3 5.3 1.6 7.0 NA 2.9 1.8 4.2 NA NA 2.0 3.9 5.9 78.7 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 13.5 1.5 1.7 16.6 3.7 4.7 3.5 11.9 3.4 2.3 5.8 9.7 2.7 1.2 2.6 2.5 9.0 4.8 4.0 8.9 61.9 999.3 90.8 157.3 1247.4 211.9 263.3 162.6 637.8 261.3 92.9 354.2 452.7 140.6 67.7 132.0 160.6 500.9 146.6 211.9 358.4 3551.5
1982-11-01 334.4 46.5 65.3 446.2 68.9 107.8 67.2 243.9 99.3 35.0 134.3 206.6 55.8 23.5 45.3 68.3 192.9 61.2 87.4 148.7 1372.6 291.9 22.4 38.2 352.5 78.1 63.2 82.5 223.8 107.9 29.0 136.9 114.6 43.5 17.5 38.0 40.7 139.7 40.3 57.3 97.7 1065.2 152.7 NA NA 175.4 33.8 53.2 14.9 101.9 35.5 15.9 51.4 73.4 21.5 13.2 19.2 29.7 83.6 22.7 27.6 50.4 536.0 87.0 6.5 12.2 105.7 21.0 22.7 13.1 56.8 23.6 8.0 31.6 58.5 8.8 7.8 8.8 15.8 41.2 17.3 20.9 38.2 332.1 108.7 14.2 13.8 136.7 19.0 27.4 13.2 59.6 23.8 8.8 32.6 42.4 8.4 7.9 15.7 13.9 45.9 9.6 11.1 20.8 337.9 28.0 NA NA 30.6 6.0 5.3 3.2 14.5 7.1 1.9 9.0 NA 3.1 2.0 4.7 NA NA 2.0 3.9 5.9 86.5 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 14.1 1.5 1.7 17.2 3.9 5.1 4.6 13.6 3.6 2.6 6.2 11.3 3.0 1.3 3.1 2.9 10.3 5.4 4.3 9.6 68.3 1031.9 92.3 156.5 1280.7 232.2 285.9 199.0 717.2 302.4 101.5 403.9 522.9 145.7 73.6 135.7 176.1 531.1 159.3 215.4 374.7 3830.5
1982-12-01 389.6 53.8 77.9 521.3 90.8 155.5 146.3 392.6 142.9 51.7 194.6 346.6 69.9 31.4 55.0 104.0 260.3 75.7 97.2 172.9 1888.3 334.6 29.7 43.9 408.2 87.5 90.3 143.0 320.8 148.2 39.8 188.0 208.5 57.2 21.5 56.5 57.3 192.5 45.2 64.1 109.3 1427.3 172.8 NA NA 198.0 42.6 79.0 29.4 151.0 48.8 22.1 70.9 127.9 30.9 16.2 23.8 41.5 112.4 24.5 31.1 55.7 715.9 99.1 8.6 14.5 122.1 23.8 30.3 25.4 79.6 33.4 11.7 45.1 88.9 12.9 10.5 11.1 23.1 57.6 22.8 24.8 47.6 440.9 128.5 16.2 16.0 160.7 23.0 37.6 26.6 87.2 34.8 13.1 47.9 71.9 11.8 11.0 19.6 21.5 63.9 13.4 12.4 25.7 457.4 32.7 NA NA 35.7 7.7 7.9 6.0 21.7 11.1 2.6 13.8 NA 4.6 2.5 5.8 NA NA 2.4 4.3 6.7 118.6 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 16.5 1.6 1.9 20.0 4.2 8.0 7.4 19.7 4.7 3.5 8.2 18.5 4.9 1.8 3.9 4.1 14.6 6.9 4.3 11.2 92.2 1190.4 111.0 182.3 1483.7 281.2 410.7 385.0 1077.0 426.1 145.2 571.4 889.3 194.0 95.8 176.7 258.7 725.2 192.6 240.5 433.1 5179.7
1983-01-01 311.4 43.8 65.1 420.3 58.0 95.1 66.6 219.7 78.5 31.4 109.8 135.3 50.1 20.7 47.4 63.9 182.1 54.2 93.0 147.2 1214.5 270.7 22.9 36.0 329.6 58.8 55.5 64.3 178.6 81.6 25.0 106.6 81.5 43.7 15.6 34.1 35.8 129.3 36.9 57.7 94.6 920.3 146.9 NA NA 169.3 28.8 50.1 14.1 92.9 29.7 14.9 44.6 64.0 22.8 12.0 17.7 27.8 80.4 20.5 30.7 51.2 502.4 82.7 7.1 12.5 102.3 19.7 18.8 9.2 47.7 20.0 6.4 26.4 43.5 8.0 6.7 8.1 13.9 36.6 15.3 24.2 39.5 295.9 94.6 15.7 12.1 122.3 16.6 25.8 9.6 52.0 18.8 7.2 26.0 35.6 7.4 6.7 14.3 11.4 39.8 8.0 11.6 19.6 295.4 26.8 NA NA 29.3 4.7 4.7 2.6 12.0 5.3 1.5 6.8 NA 2.9 1.7 3.9 NA NA 1.9 3.6 5.5 75.2 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 12.0 1.0 1.6 14.6 3.0 4.3 3.3 10.6 2.7 1.9 4.6 7.4 2.5 1.0 2.5 2.1 8.1 3.8 3.9 7.7 53.0 959.3 91.7 151.9 1202.8 190.7 255.4 169.9 615.9 237.7 88.8 326.5 379.2 138.6 64.9 128.5 159.3 491.4 141.8 226.9 368.6 3384.5
1983-02-01 327.2 39.3 62.3 428.8 63.7 105.1 59.2 228.0 72.9 29.4 102.3 144.2 64.7 22.1 44.0 64.8 195.5 56.7 85.1 141.8 1240.6 278.4 20.8 35.4 334.6 59.7 60.2 64.6 184.5 73.5 23.4 96.9 86.6 44.3 16.3 34.0 36.4 130.9 38.0 50.2 88.2 921.7 149.3 NA NA 170.5 26.2 47.5 12.3 86.0 25.2 12.6 37.9 53.5 20.2 11.5 17.0 25.8 74.5 19.7 27.9 47.6 470.0 85.3 6.4 11.7 103.5 18.9 19.8 8.5 47.2 17.3 5.9 23.2 39.7 8.9 6.4 7.1 13.0 35.4 13.9 21.2 35.1 284.1 100.6 13.3 12.3 126.2 16.7 24.9 9.6 51.1 18.0 7.0 25.0 33.2 7.4 6.6 13.2 11.2 38.4 7.9 10.7 18.6 292.6 26.9 NA NA 29.3 5.0 4.5 2.4 11.9 5.6 1.7 7.3 NA 3.2 1.9 3.8 NA NA 2.0 3.3 5.3 76.5 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 12.8 1.1 1.6 15.5 3.3 4.4 2.6 10.3 2.7 1.9 4.6 8.0 3.0 1.0 2.5 2.1 8.6 4.2 3.9 8.2 55.1 995.5 82.0 146.7 1224.2 194.8 267.5 159.4 621.7 216.4 82.3 298.7 378.0 152.8 66.4 122.1 157.9 499.1 143.7 204.4 348.1 3369.8
1983-03-01 350.9 43.4 65.7 460.0 66.0 124.1 67.3 257.5 93.3 34.2 127.5 180.5 63.1 24.9 47.7 70.0 205.7 60.9 83.7 144.6 1375.7 303.8 23.5 39.1 366.4 71.6 67.6 73.9 213.0 100.6 28.2 128.8 108.0 48.3 16.8 36.7 39.1 140.9 37.0 55.0 92.0 1049.2 162.4 NA NA 185.8 30.1 58.6 16.6 105.3 31.1 15.2 46.3 64.4 20.9 13.3 18.9 30.4 83.4 21.8 28.8 50.5 535.7 95.9 6.9 14.0 116.8 22.9 24.1 9.9 56.8 23.5 7.6 31.2 54.4 9.8 7.7 7.8 15.3 40.5 16.2 24.6 40.8 340.5 107.6 15.4 13.7 136.7 18.0 28.2 10.1 56.3 19.7 7.5 27.2 37.6 7.3 7.3 14.8 12.2 41.6 8.7 11.6 20.3 319.6 29.8 NA NA 32.6 6.0 5.7 3.0 14.7 6.5 1.9 8.5 NA 3.5 2.1 4.2 NA NA 2.3 3.4 5.7 89.1 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 13.8 1.1 1.8 16.7 3.6 5.3 3.1 12.0 3.8 2.5 6.3 10.6 3.1 1.1 2.6 2.2 9.1 4.0 4.4 8.5 63.1 1080.8 91.4 160.3 1332.4 219.8 315.1 184.2 719.1 279.7 97.5 377.2 472.1 157.3 73.7 133.2 174.4 538.7 151.9 213.9 365.8 3805.3
1983-04-01 323.4 43.7 61.9 429.0 58.3 112.3 57.7 228.2 111.2 39.4 150.6 199.4 51.1 24.5 52.9 65.3 193.7 63.5 79.7 143.2 1344.2 301.9 21.7 35.6 359.2 56.2 62.9 61.5 180.7 105.6 28.6 134.1 115.3 37.0 16.0 33.6 33.8 120.5 35.1 50.2 85.2 994.9 156.8 NA NA 177.8 29.3 51.3 11.1 91.7 33.1 14.8 47.8 69.3 18.3 12.5 17.4 25.9 74.1 21.3 27.0 48.3 509.0 91.0 6.2 12.9 110.1 23.0 20.7 9.3 53.0 23.3 8.2 31.5 53.0 10.5 7.5 7.3 14.8 40.1 16.7 21.6 38.3 326.0 105.2 12.4 12.8 130.3 16.4 26.3 10.1 52.9 22.2 8.2 30.4 39.7 7.4 7.3 13.7 12.1 40.5 8.8 10.4 19.2 313.0 28.0 NA NA 30.6 5.6 5.4 2.5 13.5 6.9 2.0 8.9 NA 3.1 2.1 3.9 NA NA 2.4 3.1 5.5 83.5 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 14.3 1.3 1.7 17.2 3.4 4.0 3.1 10.6 4.7 2.7 7.4 11.7 2.6 1.1 2.2 2.3 8.2 4.4 3.7 8.2 63.3 1036.4 86.4 148.1 1270.9 193.5 284.2 155.7 633.4 308.3 104.2 412.5 503.4 131.2 71.5 131.8 159.3 493.8 153.0 198.1 351.1 3665.1
1983-05-01 316.6 42.3 63.7 422.6 67.8 120.5 64.9 253.2 112.5 41.4 153.9 200.5 54.8 25.4 55.0 68.9 204.1 64.5 81.1 145.6 1379.9 281.5 21.4 36.4 339.2 62.0 67.0 65.2 194.2 101.9 28.4 130.3 112.1 40.1 16.1 36.6 35.0 127.8 34.1 52.7 86.8 990.4 159.8 NA NA 181.3 35.1 53.6 12.0 100.7 33.9 15.6 49.5 69.3 20.2 12.7 18.0 26.9 77.8 21.3 27.5 48.9 527.5 91.6 6.1 13.1 110.8 26.8 22.5 10.5 59.8 24.5 8.1 32.6 56.0 11.4 7.7 8.1 15.3 42.4 16.3 23.2 39.5 341.1 106.9 12.7 13.2 132.8 19.6 29.4 11.1 60.2 25.0 9.1 34.0 46.0 8.3 7.8 14.2 12.9 43.2 9.1 11.4 20.5 336.8 27.5 NA NA 30.2 6.2 5.6 3.0 14.7 7.0 1.9 8.9 NA 3.1 2.1 3.9 NA NA 2.2 3.6 5.8 85.1 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 14.1 1.4 1.8 17.3 3.7 4.8 3.1 11.6 4.6 2.8 7.3 11.5 2.8 1.1 2.3 2.3 8.5 4.3 5.0 9.3 65.6 1014.2 85.0 152.4 1251.7 222.9 304.9 170.1 697.9 310.8 107.7 418.5 510.6 142.0 73.5 138.9 166.5 520.8 153.2 207.4 360.5 3760.0
1983-06-01 325.4 40.4 64.9 430.6 64.2 115.0 58.6 237.8 103.6 37.1 140.7 175.2 52.3 24.6 56.2 65.7 198.8 63.0 79.7 142.8 1325.8 290.6 20.8 34.2 345.6 57.0 66.2 60.2 183.3 90.3 25.6 115.9 100.1 38.2 16.1 35.9 33.7 123.8 34.9 46.4 81.3 950.0 158.8 NA NA 180.2 30.9 53.6 12.0 96.5 34.0 15.5 49.5 72.6 19.8 12.6 18.7 26.8 77.9 21.0 26.5 47.5 524.2 94.0 6.2 13.1 113.2 28.5 22.9 9.8 61.2 22.4 7.4 29.8 51.9 11.3 7.4 7.7 14.9 41.3 15.7 21.9 37.6 335.0 106.9 13.7 13.4 134.0 18.4 25.8 11.0 55.2 22.2 8.1 30.3 37.8 7.2 7.2 14.1 12.2 40.6 8.6 10.4 19.0 316.9 27.3 NA NA 30.2 6.4 5.2 2.5 14.1 6.7 1.9 8.6 NA 2.9 2.0 4.2 NA NA 2.2 3.5 5.7 83.0 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 14.2 1.4 2.0 17.6 3.4 4.3 2.6 10.3 3.9 2.3 6.2 10.1 2.8 1.0 2.2 2.1 8.2 4.3 5.6 9.9 62.3 1033.9 83.7 151.6 1269.3 210.5 294.4 157.0 661.8 284.6 98.3 383.0 462.4 136.0 71.3 139.7 160.3 507.3 150.7 196.4 347.1 3630.8
1983-07-01 323.1 41.6 69.5 434.2 60.8 111.7 58.8 231.3 97.4 34.1 131.5 181.4 57.7 23.9 54.6 66.9 203.0 61.9 84.7 146.6 1328.1 297.6 21.3 36.2 355.2 54.9 64.0 59.9 178.8 95.1 26.6 121.7 103.4 39.0 16.2 36.9 34.2 126.4 35.8 49.8 85.6 971.0 162.9 NA NA 185.1 32.9 55.0 14.4 102.2 33.5 16.0 49.5 65.9 20.8 13.0 19.5 29.0 82.2 22.1 27.8 49.9 534.8 98.3 6.2 13.5 118.0 25.7 22.2 11.1 58.9 24.0 7.9 31.9 51.7 8.3 8.1 8.3 15.8 40.5 18.2 23.1 41.3 342.3 106.2 13.9 13.1 133.2 18.4 30.2 9.7 58.3 24.7 8.4 33.0 40.3 7.6 7.7 14.3 12.3 41.8 8.9 10.9 19.8 326.5 28.3 NA NA 31.3 5.9 5.1 2.7 13.7 6.0 1.8 7.8 NA 2.9 2.0 4.0 NA NA 2.2 4.4 6.7 83.9 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 13.6 1.5 2.1 17.2 3.8 4.2 2.8 10.8 4.0 2.5 6.5 10.4 3.0 1.1 2.3 2.3 8.7 4.6 6.3 10.8 64.5 1047.4 85.9 159.5 1292.8 203.9 293.4 159.6 656.9 286.2 97.7 384.0 468.3 141.0 72.5 140.9 165.6 519.9 154.7 209.8 364.5 3686.5
1983-08-01 338.1 42.2 67.9 448.2 64.8 117.2 64.8 246.9 96.3 34.0 130.2 179.7 61.5 25.0 54.6 70.4 211.5 64.7 85.2 149.9 1366.3 309.6 22.6 37.1 369.3 58.8 72.4 65.2 196.4 91.3 25.7 117.0 101.4 47.1 17.2 39.3 37.3 140.9 37.1 53.3 90.5 1015.5 167.3 NA NA 189.4 35.1 61.0 14.0 110.1 36.6 16.4 52.9 60.4 21.2 13.9 22.1 29.5 86.7 22.8 28.7 51.5 551.0 101.7 6.7 13.8 122.1 27.8 24.9 11.2 63.9 23.0 7.9 30.9 54.0 9.0 8.5 8.5 16.3 42.3 18.6 24.6 43.2 356.4 111.9 14.2 13.5 139.6 19.4 34.2 11.0 64.6 24.1 8.4 32.4 38.0 8.9 8.2 15.3 13.1 45.5 9.2 11.7 20.8 340.9 29.6 NA NA 32.6 6.4 5.8 3.1 15.3 6.5 1.9 8.3 NA 2.9 2.2 4.0 NA NA 2.5 4.7 7.1 88.1 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 13.8 1.5 1.8 17.1 3.8 4.1 2.8 10.7 3.6 2.4 6.0 10.0 3.2 1.1 2.5 2.4 9.2 4.9 4.5 9.4 62.5 1089.4 88.5 159.1 1337.0 217.7 320.9 172.4 711.0 283.0 96.9 379.9 458.2 155.8 76.5 147.3 174.6 554.2 160.8 215.2 376.0 3816.3
1983-09-01 330.6 42.5 67.5 440.6 65.1 106.9 68.7 240.7 105.6 37.2 142.9 185.0 61.0 24.5 53.8 71.6 210.9 66.3 84.3 150.6 1370.8 310.2 22.4 37.4 370.0 57.4 69.7 66.4 193.6 94.7 26.5 121.3 105.2 46.1 16.9 38.3 37.2 138.5 36.8 54.0 90.8 1019.2 163.9 NA NA 185.1 34.6 55.0 15.1 104.7 37.0 17.5 54.5 73.9 20.5 13.4 21.5 29.6 85.1 22.8 27.7 50.5 553.9 99.1 7.0 13.4 119.5 25.8 22.8 12.3 61.0 24.4 8.2 32.6 52.3 9.1 8.3 8.2 16.4 42.0 18.4 23.8 42.3 349.7 111.3 14.8 13.2 139.3 19.6 30.1 12.1 61.9 25.6 9.2 34.8 40.3 7.6 8.2 15.2 13.6 44.5 9.8 11.7 21.5 342.3 29.2 NA NA 32.1 6.4 5.3 3.2 14.9 6.0 1.9 7.9 NA 2.9 2.0 4.2 NA NA 2.3 5.0 7.4 88.0 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 13.5 1.5 2.1 17.1 3.8 4.0 3.1 10.9 3.6 2.5 6.1 10.3 3.2 1.0 2.3 2.4 8.9 4.5 6.4 10.9 64.1 1075.6 89.6 157.7 1322.8 213.9 295.1 181.4 690.3 298.5 103.5 402.0 482.7 152.4 74.9 144.6 176.0 547.9 162.0 215.6 377.6 3823.4
1983-10-01 351.1 45.0 66.0 462.1 66.3 114.4 84.1 264.8 97.9 37.3 135.2 194.4 56.9 24.6 55.6 74.9 212.0 63.7 80.1 143.8 1412.3 314.5 22.9 37.0 374.4 59.9 73.5 71.3 204.8 102.9 29.1 132.0 106.4 46.9 18.2 38.4 39.1 142.7 39.6 53.1 92.7 1053.0 167.2 NA NA 189.6 36.4 52.6 14.7 103.7 33.1 16.2 49.3 65.5 21.1 13.2 20.9 29.5 84.7 22.9 29.4 52.4 545.1 96.7 7.2 12.7 116.6 21.9 22.7 10.2 54.8 22.5 7.6 30.0 51.5 8.4 8.0 8.7 15.2 40.3 17.8 21.6 39.4 332.8 112.3 15.1 13.0 140.4 17.8 26.8 12.8 57.4 24.2 9.1 33.3 41.5 8.5 7.9 15.9 13.9 46.2 10.1 11.6 21.7 340.5 29.9 NA NA 33.0 6.3 4.9 3.3 14.5 6.4 1.9 8.4 NA 3.2 2.1 4.0 NA NA 2.5 5.1 7.5 88.7 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 16.6 1.5 2.4 20.5 3.4 5.0 3.3 11.7 3.4 2.5 5.9 11.2 3.1 1.3 2.3 2.7 9.4 5.5 7.2 12.8 71.4 1105.9 93.1 156.4 1355.4 213.3 301.1 200.2 714.6 291.8 104.0 395.8 485.3 149.9 75.8 146.9 180.8 553.5 163.1 211.0 374.1 3878.7
1983-11-01 361.5 45.8 67.2 474.5 72.8 136.5 101.2 310.4 110.2 41.0 151.2 224.9 59.3 27.8 57.7 83.4 228.2 69.4 82.9 152.3 1541.6 336.8 24.0 38.4 399.1 64.3 80.3 82.8 227.4 109.7 30.0 139.6 123.1 48.9 19.4 40.7 42.6 151.7 42.0 53.9 95.8 1136.8 175.6 NA NA 198.2 37.2 61.7 16.7 115.6 37.6 17.5 55.1 77.6 23.3 14.6 22.1 32.3 92.2 24.6 29.9 54.5 593.3 101.2 7.6 12.8 121.6 24.2 27.0 11.8 63.0 24.6 7.9 32.5 64.3 9.2 8.6 8.6 16.1 42.5 18.2 21.8 40.1 363.9 115.0 15.4 13.2 143.7 18.8 31.4 15.5 65.7 26.0 9.7 35.7 47.9 9.2 8.8 16.4 15.5 49.8 10.8 11.7 22.5 365.3 31.5 NA NA 34.7 7.2 6.2 3.4 16.8 7.0 2.1 9.1 NA 3.4 2.3 4.0 NA NA 2.8 5.2 8.0 97.7 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 17.3 1.5 2.4 21.1 4.0 5.5 3.6 13.1 3.7 2.8 6.5 12.6 3.3 1.5 2.8 3.2 10.8 6.7 7.1 13.8 78.0 1155.9 95.4 159.6 1410.9 230.1 350.1 235.3 815.5 320.3 111.4 431.7 568.7 158.3 83.7 153.3 198.8 594.1 175.3 215.3 390.6 4211.5

Select one of the time series as follows (but replace the column name with your own chosen column):

myts <- ts(retaildata[,“A3349873A”],frequency=12, start=c(1982,4))

I have selected “A3349337W” as the timeseries from the retail data set for this exercise.

myts <- ts(retaildata[,"A3349337W"],frequency=12, start=c(1982,4))

myts
##        Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov
## 1982                    53.6  55.4  48.4  52.1  54.2  53.6  58.0  67.2
## 1983  66.6  59.2  67.3  57.7  64.9  58.6  58.8  64.8  68.7  84.1 101.2
## 1984  73.7  69.6  77.7  68.5  70.0  60.5  60.2  70.0  69.5  81.5  96.5
## 1985  69.4  69.8  74.1  71.9  83.6  68.8  71.8  79.4  76.0  97.0 126.8
## 1986  90.3  89.8  89.6  91.9  96.0  89.3  79.4  89.1  88.1 116.8 128.6
## 1987 103.9  97.3  97.9  97.2 106.5  88.2  97.7 100.2 110.8 137.3 150.5
## 1988 126.6 119.4 123.6 108.8 121.0 113.9 110.9 124.3 118.5 143.9 172.1
## 1989 160.7 155.2 161.0 149.3 165.6 140.1 128.2 140.4 130.2 143.3 185.3
## 1990  96.4  95.0 103.8  97.1 104.6 100.7  98.2 106.6  96.7 113.3 126.2
## 1991  89.1  99.6 129.0 125.6 127.3 111.7 114.1 118.0 119.6 121.5 128.5
## 1992 100.1 108.2 113.2 108.0  98.2  95.2 101.4  93.5 112.0 118.9 125.7
## 1993 100.7 102.8 113.5  99.2  95.4  89.3  84.4  91.1 102.2 101.4 108.5
## 1994 111.0 121.4 125.6 116.2 125.1 119.1 117.5 123.8 134.5 141.0 145.2
## 1995 120.8 121.0 132.6 116.3 113.2 120.2 124.3 134.0 140.6 163.7 176.2
## 1996 157.5 147.7 158.1 152.4 171.0 158.0 174.0 157.5 167.0 181.0 189.6
## 1997 168.0 154.9 169.9 159.8 172.7 154.1 144.9 141.3 164.3 162.7 172.8
## 1998 157.0 145.0 158.6 145.9 146.8 140.2 135.8 141.7 158.7 148.4 148.0
## 1999 133.1 120.5 132.2 126.0 141.0 135.0 143.7 144.4 171.7 185.5 167.9
## 2000 169.7 163.2 167.6 148.7 161.4 188.5 158.3 174.5 193.2 194.5 209.7
## 2001 209.6 185.2 202.2 200.0 200.3 200.3 193.6 211.4 218.2 236.3 230.6
## 2002 219.9 196.6 218.7 216.8 205.5 198.2 233.9 246.2 259.8 277.3 294.3
## 2003 247.0 229.3 250.3 241.6 247.0 258.7 271.3 291.1 312.7 324.6 315.2
## 2004 258.9 246.5 260.9 249.0 256.5 257.4 275.4 269.8 279.8 307.3 323.9
## 2005 281.8 250.6 274.1 270.3 268.2 264.0 266.9 298.6 303.1 329.4 345.6
## 2006 288.0 277.3 302.8 288.5 290.4 275.4 262.4 272.9 279.7 299.3 313.3
## 2007 286.4 268.4 286.6 260.0 273.0 248.5 259.7 272.2 293.6 294.9 294.3
## 2008 263.0 246.2 255.2 240.2 239.6 226.9 238.7 253.1 271.3 283.1 299.0
## 2009 289.3 249.6 272.1 272.9 279.4 267.8 273.1 307.7 318.2 334.0 325.0
## 2010 309.2 272.6 311.1 298.2 313.1 305.8 307.3 330.9 362.8 361.7 364.2
## 2011 311.6 283.7 322.2 310.8 319.5 305.1 308.9 355.6 384.9 401.1 382.1
## 2012 334.0 292.1 309.6 305.8 325.0 314.2 327.2 363.7 406.9 397.1 379.6
## 2013 340.0 293.9 330.7 290.7 291.8 281.1 309.8 344.6 360.7 384.7 367.9
##        Dec
## 1982 146.3
## 1983 192.3
## 1984 179.4
## 1985 221.2
## 1986 235.4
## 1987 248.8
## 1988 307.4
## 1989 228.9
## 1990 159.5
## 1991 151.4
## 1992 154.7
## 1993 179.0
## 1994 180.7
## 1995 225.4
## 1996 249.8
## 1997 248.7
## 1998 183.0
## 1999 200.7
## 2000 266.3
## 2001 291.0
## 2002 341.9
## 2003 360.8
## 2004 361.1
## 2005 395.2
## 2006 341.6
## 2007 339.3
## 2008 360.2
## 2009 348.9
## 2010 395.4
## 2011 409.0
## 2012 428.0
## 2013 430.7
title <- 'Retail Sales for Category = A3349337W'

# Timeseries plot before Transformation:
plot <- autoplot(myts,ylab="$ Sales Turnover",xlab="Year") + ggtitle(title)

lambda <- BoxCox.lambda(myts)
cat('BoxCox Transofrmation Parameter, Lambda:', lambda)
## BoxCox Transofrmation Parameter, Lambda: 0.9165544
# Timeseries plot after applying BoxCox Transformation:
plot_boxcox <- autoplot(BoxCox(myts,lambda),ylab="$ Sales Turnover",xlab="Year") + ggtitle(paste(title," (w/ BoxCox Transformation)"))

grid.arrange(plot,plot_boxcox, ncol=2) 

Section 3.7 - Exercise 8

For your retail time series (from Exercise 3 in Section 2.10):

  1. Split the data into two parts using - myts.train <- window(myts, end=c(2010,12)) myts.test <- window(myts, start=2011)
myts.train <- window(myts, end=c(2010,12))
myts.test <- window(myts, start=2011)
  1. Check that your data have been split appropriately by producing the following plot - autoplot(myts) + autolayer(myts.train, series=“Training”) + autolayer(myts.test, series=“Test”)
autoplot(myts) +
  autolayer(myts.train, series="Training") +
  autolayer(myts.test, series="Test")

  1. Calculate forecasts using snaive applied to myts.train - fc <- snaive(myts.train)
fc <- snaive(myts.train)

fc %>% kable() %>% kable_styling(bootstrap_options = c("striped", "hover", "condensed", "responsive")) %>% scroll_box(width="100%",height="300px")
Point Forecast Lo 80 Hi 80 Lo 95 Hi 95
Jan 2011 309.2 275.4855 342.9145 257.6381 360.7619
Feb 2011 272.6 238.8855 306.3145 221.0381 324.1619
Mar 2011 311.1 277.3855 344.8145 259.5381 362.6619
Apr 2011 298.2 264.4855 331.9145 246.6381 349.7619
May 2011 313.1 279.3855 346.8145 261.5381 364.6619
Jun 2011 305.8 272.0855 339.5145 254.2381 357.3619
Jul 2011 307.3 273.5855 341.0145 255.7381 358.8619
Aug 2011 330.9 297.1855 364.6145 279.3381 382.4619
Sep 2011 362.8 329.0855 396.5145 311.2381 414.3619
Oct 2011 361.7 327.9855 395.4145 310.1381 413.2619
Nov 2011 364.2 330.4855 397.9145 312.6381 415.7619
Dec 2011 395.4 361.6855 429.1145 343.8381 446.9619
Jan 2012 309.2 261.5205 356.8795 236.2804 382.1196
Feb 2012 272.6 224.9205 320.2795 199.6804 345.5196
Mar 2012 311.1 263.4205 358.7795 238.1804 384.0196
Apr 2012 298.2 250.5205 345.8795 225.2804 371.1196
May 2012 313.1 265.4205 360.7795 240.1804 386.0196
Jun 2012 305.8 258.1205 353.4795 232.8804 378.7196
Jul 2012 307.3 259.6205 354.9795 234.3804 380.2196
Aug 2012 330.9 283.2205 378.5795 257.9804 403.8196
Sep 2012 362.8 315.1205 410.4795 289.8804 435.7196
Oct 2012 361.7 314.0205 409.3795 288.7804 434.6196
Nov 2012 364.2 316.5205 411.8795 291.2804 437.1196
Dec 2012 395.4 347.7205 443.0795 322.4804 468.3196
# Calculating Forecast applying BoxCox transformation
fc1 <- snaive(myts.train, lambda = lambda)

#fc1 %>% kable() %>% kable_styling(bootstrap_options = c("striped", "hover", "condensed", "responsive")) %>% scroll_box(width="100%",height="300px")

# Calculating Forecast applying BoxCox transformation
fc2 <- snaive(myts.train, lambda = lambda, biasadj = TRUE)

autoplot(myts.train) +
  autolayer(fc, series="Without Transformation") +
  autolayer(fc1, series="Simple Back Transformation", PI=FALSE) +
  autolayer(fc2, series="Bias Adjusted", PI=FALSE) +
  guides(colour=guide_legend(title="Forecast"))

  1. Compare the accuracy of your forecasts against the actual values stored in myts.test - accuracy(fc,myts.test)
accuracy(fc,myts.test)
##                     ME     RMSE      MAE      MPE      MAPE      MASE
## Training set  9.460661 26.30758 21.23363 4.655690 12.762886 1.0000000
## Test set     17.212500 21.26067 17.39583 4.748234  4.807728 0.8192584
##                   ACF1 Theil's U
## Training set 0.8070166        NA
## Test set     0.4843871 0.6934111
# With BoxCox Transformation
accuracy(fc1,myts.test)
##                     ME     RMSE      MAE      MPE      MAPE      MASE
## Training set  9.460661 26.30758 21.23363 4.655690 12.762886 1.0000000
## Test set     17.212500 21.26067 17.39583 4.748234  4.807728 0.8192584
##                   ACF1 Theil's U
## Training set 0.8070166        NA
## Test set     0.4843871 0.6934111
  1. Check the residuals - checkresiduals(fc)

Q. Do the residuals appear to be uncorrelated and normally distributed?

checkresiduals(fc)

## 
##  Ljung-Box test
## 
## data:  Residuals from Seasonal naive method
## Q* = 856.11, df = 24, p-value < 2.2e-16
## 
## Model df: 0.   Total lags used: 24

Analysis of Residuals:

  • Time plot shows that residuals show variations, residual values are not mostly zeros and does not show any seasonal patter.
  • From the ACF plot, residuals seem to have high positive autocorrelation between r1 to r10. So based on Box-Pierce test, Q statistic (\(Q=T\sum _{ k=1 }^{ h }{ { { r }_{ k } }^{ 2 } }\)) using h=10 for non-seasonal residual data, seems to have a relatively high value showing strong correlation amongst residuals.
  • From the Histogram, it is clear that the mean of the residuals is not zero and residuals are also not normally distributed.
  • Based on the outpout of Ljung-Box test, \({ Q }^{ * }\) statistic (\({ Q }^{ * }=T(T+2)\sum _{ k=1 }^{ h }{ { { { (T-k) }^{ -1 }r }_{ k } }^{ 2 } }\)) shows significantly high value with very small p-value. This suggests that the residual autocorrelations DO NOT come from white noise series. Hence it can be concluded that the residuals show sufficient correlation.
  1. Q. How sensitive are the accuracy measures to the training/test split?

The approach to gauge sensitivity of accuracy measures to the training/test split would be to iterate over multiple years as splitting point and verify the impact on the measures.

calcAccuracy <- function(year){
  train <- window(myts, end=c(year, 12))
  test <- window(myts, start=year+1)
  model_accuracy <- accuracy(snaive(train), test)
  return(model_accuracy)
}

splitYears <- c(2005:2011)

modelAccuracyDF <- data.frame()
for (year in splitYears){
  currentAccuracy <- calcAccuracy(year)
  testRow <- data.frame(t(currentAccuracy[2,]))
  modelAccuracyDF <- rbind(modelAccuracyDF, testRow)
}
row.names(modelAccuracyDF) <- paste('Dec',splitYears,sep = '-')
modelAccuracyDF <- tibble::rownames_to_column(modelAccuracyDF, "Split_Period")
modelAccuracyDF %>% kable() %>% kable_styling(bootstrap_options = c("striped", "hover", "condensed", "responsive")) %>% scroll_box(width="100%",height="300px")
Split_Period ME RMSE MAE MPE MAPE MASE ACF1 Theil.s.U
Dec-2005 -9.4625000 26.79323 22.22083 -3.0565350 7.532356 1.0803141 0.6458613 1.2908423
Dec-2006 -17.9083333 25.60143 20.61667 -7.1891576 8.014002 0.9961769 0.5989406 1.1544668
Dec-2007 -1.6375000 22.04366 19.97083 -1.3680734 7.258093 0.9818795 0.7868247 0.9620150
Dec-2008 46.5541667 52.76536 47.49583 14.7565145 15.026410 2.3323712 0.6436880 2.2893119
Dec-2009 39.6166667 41.75055 39.61667 11.6729690 11.672969 1.9047330 0.4997840 1.4503696
Dec-2010 17.2125000 21.26067 17.39583 4.7482337 4.807728 0.8192584 0.4843871 0.6934111
Dec-2011 0.8666667 16.47723 14.34167 0.0508195 4.245806 0.6839372 0.4736556 0.4855843
ggplot(modelAccuracyDF,aes(x=Split_Period)) +
  geom_line(aes(y = RMSE, color = "blue"),group=1,size=2 ) +
  geom_line(aes(y = MAPE, color = "red"),group=1,size=2) +
  geom_line(aes(y = MAE, color = "green"),group=1,size=2) +
  geom_line(aes(y = MASE, color = "orange"),group=1,size=2) +
  xlab('Train/Test Split Period') +
  ylab('Measure Value') +
  scale_color_discrete(name = "Accuracy Measures", labels = c("RMSE","MAPE","MAE","MASE")) +
  ggtitle("Train/Test Split Accuracy Measures Sensitivity")

From the table and chart above, we can clearly see that choice of Training/Test split point impacts the accuracy measures for the test data sets. Also, it appears that Dec’2011 is the best choice for the split with lowest RMSE, MAE, MAPE and MASE etc. values.