* Stata
scatter y x                     // 先画散点图判断线性
pwcorr x y, sig                 // Pearson r 及 p 值
spearman x y                    // Spearman ρ
regress y x                     // 简单线性回归

## R
plot(df$x, df$y)
cor.test(df$x, df$y, method = "pearson")
cor.test(df$x, df$y, method = "spearman")
fit <- lm(y ~ x, data = df); summary(fit)