如何从一步回归中提取公式？

Question

I'm running a step regression and I'd like to extract the final formula to use it in another regression. 我正在进行逐步回归，我想提取最终公式，以便在另一个回归中使用它。

Using this example: 使用此示例：

lm1 <- lm(Fertility ~ ., data = swiss)
slm1 <- step(lm1)

I would expect to be able to assign this to a formula object: 我希望能够将其分配给公式对象：

Fertility ~ Agriculture + Education + Catholic + 
    Infant.Mortality

Answer 1

You can simply extract it from your slm1 object using the formula method for lm object 您可以使用lm对象的formula方法从slm1对象中简单地提取它

formula(slm1)
Fertility ~ Agriculture + Education + Catholic + Infant.Mortality

Answer 2

Got it: 得到它了：

> as.formula(slm1$call)
Fertility ~ Agriculture + Education + Catholic + Infant.Mortality