3.2.4. Correlation Analysis

This analysis aims to explore the influence of the former expansion of Qingtu Lake on the secondary vegetation coverage around Qingtu Lake after ecological water transfer. The two variables are one-to-one, corresponding, and relatively continuous, so the Pearson correlation coe fficient was selected for calculation. The equation is given below [39].

$$\mathbf{r} = \frac{\sum \left(\mathbf{X} - \mathbf{X}\right)\left(\mathbf{Y} - \mathbf{Y}\right)}{\sqrt{\sum \left(\mathbf{X} - \mathbf{X}\right)^2 \sum \left(\mathbf{Y} - \mathbf{Y}\right)^2}}\tag{4}$$

where X and Y represent the two groups of variables, and X and Y represent the average values of the two groups of variables. If r is greater than 0, then a positive correlation between the two variables is indicated; if the contrary, there is a negative correlation. In addition, the greater the absolute value of r, the stronger the correlation between the two variables.
