Shapley Value Analysis of Yield Prediction Across Years: Impact of VTCI Stages on Crop Production

The given data represents a double y-axis graph with the x-axis representing the years from 2011 to 2021. The left y-axis represents the average Shapley values for 24 counties for each year, while the right y-axis represents the predicted average yield values for the same 24 counties.

To analyze the Shapley values and their impact on different years, let's consider the four features: VTCI at the green-up stage, VTCI at the jointing stage, VTCI at the heading-filling stage, and VTCI at the milk maturity stage.

For the year 2013, which is considered a low-yield year, the Shapley values for all four features show negative values. This indicates that these features had a negative impact on the yield during that year. Specifically, VTCI at the green-up stage and VTCI at the heading-filling stage had the highest negative Shapley values, suggesting that these two features had the most significant adverse effect on the yield. The negative Shapley values for VTCI at the jointing stage and VTCI at the milk maturity stage were relatively smaller but still contributed to the overall decrease in yield.

Moving on to the year 2018, which is considered a moderate-yield year, the Shapley values for VTCI at the green-up stage and VTCI at the jointing stage are negative but smaller in magnitude compared to 2013. This indicates that these two features still had a negative impact on the yield but to a lesser extent. On the other hand, the Shapley values for VTCI at the heading-filling stage and VTCI at the milk maturity stage turned positive, suggesting a positive contribution to the yield. However, the positive impact of these two features was not strong enough to outweigh the negative impact of the other two features.

Lastly, let's analyze the year 2021, which is considered a high-yield year. In this year, all four features, represented by their respective Shapley values, have positive values. This indicates that all the features had a positive impact on the yield, with VTCI at the green-up stage and VTCI at the milk maturity stage showing the highest positive Shapley values. These two features played a crucial role in achieving the high yield during that year.

In summary, the analysis of the Shapley values for the four features across different years provides insights into their impact on yield. The negative Shapley values for all features in the low-yield year 2013 indicate their adverse effect on the yield. The moderate-yield year 2018 showed a mixed contribution, with some features having a positive impact while others still had a negative impact. The high-yield year 2021 demonstrated the positive contribution of all features, with some features playing a more significant role in achieving the high yield.

Overall, the Shapley values analysis helps understand the relative importance of different features and their impact on the yield in different years. This information can be valuable for identifying key factors influencing yield and making informed decisions to optimize agricultural practices in the future.