使用ggplot2的交互图(interaction plot using ggplot2)

 以下代码显示了使用effects库的交互图： 
 
model <- lm(mpg ~ hp + wt + hp:wt, data=mtcars)
library(effects)
plot(effect("hp:wt", model, list(wt=c(2.2,3.2,4.2))), multiline=TRUE)
 
 
 我尝试制作相同的模型，但保持wt为2.2，但这个模型无法计算wt的系数： 
 
mtcars$wt_2.2 <- 2.2
model2.2 <- lm(mpg ~ hp + wt_2.2 + hp:wt, data=mtcars)
coef(model2.2)
 
 如何使用ggplot2制作相同的图？ 

The following code shows an interaction plot using the effects library:
 
model <- lm(mpg ~ hp + wt + hp:wt, data=mtcars)
library(effects)
plot(effect("hp:wt", model, list(wt=c(2.2,3.2,4.2))), multiline=TRUE)
 
 
I tried making the same model but holding wt at 2.2, but this model could not calculate the coefficient for wt:
 
mtcars$wt_2.2 <- 2.2
model2.2 <- lm(mpg ~ hp + wt_2.2 + hp:wt, data=mtcars)
coef(model2.2)
 
How can I make the same plot using ggplot2?

原文：https://stackoverflow.com/questions/19971972