Table A.
State space equations for each of the models in the Holt's nonlinear
| Trend | Additive Error Models | Trend | Multiplicative Error Models |
|---|---|---|---|
| N | yt = lt−1 + ɛt lt = lt−1 + αɛt | N | yt = lt−1 (1 + ɛt) lt = lt−1 (1 + αɛt) |
| A | yt = lt−1 + bt−1 + ɛt lt = lt−1 + bt−1 + αɛt bt = bt−1 + βɛt | M | yt = (lt−1 + bt−1) (1 + ɛt) lt = (lt−1 + bt−1) (1 + αɛt) bt = bt−1 + β(lt−1 + bt−1)ɛt |
| AD | yt = lt−1 + ϕbt−q + βɛt lt = lt−1 + ϕbt−1 + αɛt bt = ϕbt−1 + βɛt | MD | yt = (lt−1 + ϕbt−1) (1 + ɛt) lt = (lt−1 + ϕbt−1) (1 + αɛt) bt = ϕbt−1 + β(lt−1 + ϕbt−1)ɛt |
[i] α – smoothing factor for the level, β – smoothing factor for the trend, ϕ – damping coefficient; l – initial level components, b – initial growth components, estimated as part of the optimization problem
Table 1.
Descriptive statistics of the empirical data set
| Statistic | APPLE | BANANA | GRAPE | MANGO | PINEAPPLE |
|---|---|---|---|---|---|
| Mean | 1153.465 | 12282.65 | 889.9539 | 11091.62 | 904.2272 |
| Median | 1120.822 | 7503.050 | 414.3915 | 9559.610 | 837.1935 |
| Maximum | 2891.000 | 31504.00 | 3125.000 | 25631.00 | 1984.000 |
| Minimum | 90.00000 | 2257.000 | 70.00000 | 6988.000 | 76.00000 |
| Std. Dev. | 751.9735 | 10155.63 | 928.9188 | 4863.780 | 515.1081 |
| CV (%) | 65.1925 | 82.6827 | 104.3783 | 43.8509 | 56.9666 |
| Skewness | 0.428803 | 0.763810 | 1.081578 | 1.592267 | 0.344042 |
| Kurtosis | 2.330973 | 2.019532 | 2.922950 | 4.824546 | 2.073819 |
| Jarque–Bera (Statistic) | 2.957718 | 8.237345 | 11.71295 | 33.67557 | 3.328177 |
| Probability (Jarque–Bera test) | 0.227898 | 0.016266 | 0.002861 | 0.000000 | 0.189363 |

Figure 1.
Forecast and actual values of the five fruits using ARIMA forecasting

Figure 2.
Forecast and actual values of the five fruits using ETS forecasting
Table 2.
Unit root test results
| Fruit | Ng–Perron test | Park test | ||||
|---|---|---|---|---|---|---|
| MZa | MZt | MSB | MPT | Statistic | Critical % value | |
| APPLE | −4.655 | −1.399 | 0.287 | 18.353 | 0.473 | −2.250 |
| D (APPLE)* | −44.491 | −4.683 | 0.105 | 2.220 | −10.140 | −3.058 |
| BANANA | −1.800 | −0.841 | 0.467 | 42.823 | 0.751 | −2.302 |
| D (BANANA)* | −28.083 | −3.747 | 0.133 | 3.246 | −5.941 | −3.103 |
| GRAPE | −4.829 | −1.323 | 0.274 | 17.601 | 2.367 | −2.166 |
| D (GRAPE)* | −66.590 | −5.769 | 0.086 | 1.370 | −7.225 | −3.032 |
| PINEAPPLE | −16.870 | −2.898 | 0.171 | 5.438 | 0.063 | −2.072 |
| D (PINEAPPLE)* | −28.758 | −3.783 | 0.131 | 3.215 | −6.279 | −2.992 |
| MANGO | −1.232 | −0.429 | 0.348 | 32.137 | 3.472 | −2.342 |
| D (MANGO)* | −28.891 | −3.730 | 0.129 | 3.559 | −7.334 | −3.170 |
| Critical 5% value | −17.3 | −2.91 | 0.168 | 5.48 | ||
Table 3.
Model selection: ARIMA and Holt's nonlinear ETS model and fit criteria
| Fruit | MODEL | AIC | RMSE | MAE | MAPE | Theil | BP | VP | CVP |
|---|---|---|---|---|---|---|---|---|---|
| ARIMA | |||||||||
| APPLE | (2. 1. 0) | 13.43 | 258.97 | 215.547 | 35.440 | 0.088 | 0.387 | 0.052 | 0.560 |
| BANANA | (0. 1. 1) | 16.90 | 6026.99 | 4972.23 | 80.192 | 0.171 | 0.616 | 0.070 | 0.313 |
| GRAPE | (0. 1. 2) | 13.46 | 813.57 | 710.26 | 219.61 | 0.260 | 0.760 | 0.003 | 0.236 |
| PINEAPPLE | (0. 1. 3) | 11.83 | 113.25 | 87.964 | 11.792 | 0.053 | 0.075 | 0.004 | 0.919 |
| MANGO | (2. 2. 4) | 16.59 | 7706.93 | 6078.89 | 47.890 | 0.240 | 0.622 | 0.283 | 0.093 |
| Holt's nonlinear ETS | |||||||||
| APPLE | M M A | 842.86 | 240.93 | 147.58 | 12.97 | 0.086 | 0.014 | 0.026 | 0.95 |
| BANANA | M M A | 1032.30 | 1085.85 | 696.71 | 5.732 | 0.033 | 0.005 | 0.659 | 19.53 |
| GRAPE | M M A | 774.118 | 202.411 | 93.524 | 12.162 | 0.078 | 0.006 | 0.011 | 0.69 |
| PINEAPPLE | M A N | 763.445 | 89.846 | 60.584 | 7.219 | 0.043 | 0.005 | 0.000 | 0.138 |
| MANGO | M M N | 1038.17 | 918.334 | 520.421 | 4.014 | 0.038 | 0.022 | 0.353 | 13.84 |
Table 4.
Parameters of ETS models
| Fruit | Parameters | Initial states | |||
|---|---|---|---|---|---|
| α | β | ϕ | level | trend | |
| APPLE | 0.000 | 0.000 | 0.965 | 172.295 | 1.055 |
| BANANA | 0.165 | 0.000 | 1.000 | 2133.632 | 1.049 |
| GRAPE | 0.000 | 0.000 | 0.430 | 62.190 | 1.070 |
| PINEAPPLE | 0.944 | 0.000 | - | 39.588 | 33.480 |
| MANGO | 0.728 | 0.055 | - | 6907.784 | 0.055 |
Table 5.
Results of statistical tests to compare actual and forecast results between ARIMA and ETS models
| Fruit | Diebold–Mariano test | Giacomini–White test | Clark–West test | |||
|---|---|---|---|---|---|---|
| statistic | p | statistic | p | statistic | p | |
| APPLE | 0.235 | 0.814 | 0.116 | 0.733 | 3.734 | <0.000 |
| BANANA | 4.746 | 0.000 | 9.879 | 0.001 | 8.209 | <0.000 |
| GRAPE | 6.017 | <0.000 | 16.849 | <0.000 | 10.337 | <0.000 |
| PINEAPPLE | 2.052 | 0.046 | 3.182 | 0.074 | 4.163 | <0.000 |
| MANGO | 4.142 | <0.000 | 6.835 | 0.008 | 6.953 | <0.000 |