我试图通过将我拥有的数据分为两个子集，将两条不同的回归线（公式：工资= beta0 + beta1 D3 + beta2支出+ beta3 *（支出* D3）+ w）绘制成一个散点图下面的代码：
salary = data$salary
spending = data$spending
D1 = data$North
D2 = data$South
D3 = data$West
subsetWest = subset(data, D3 == 1)
subsetRest = subset(data, D3 == 0)
abab = lm(salary ~ 1 + spending + 1*spending, data=subsetWest) #red line
caca = lm(salary ~ 0 + spending + 0*spending, data=subsetRest) #blue line
plot(spending,salary)
points(subsetWest$spending, subsetWest$salary, pch=25, col = "red")
points(subsetRest$spending, subsetRest$salary, pch=10, col = "blue")
abline(abab, col = "red") …