adrian1121 - 13 days ago 7

R Question

I am trying to distinguish between a LM object and a RLM (robust LM from MASS) because depending on which type of regression is I want to perform one thing or another. So fitList can be either a lm or a rlm model, being all the elements of the list the same type.

*fitList* as a list of several normal linear models:

`fitList[[1]]$call`

Output: lm(formula = frmla, data = xList[[i]])

And in this second case,

`fitList[[1]][1]$call`

Output: rlm(formula = frmla, data = xList[[i]], method = "MM")

As you see, the way to obtain the formula used in both models is different. I'd like a method that distinguishes between both and tells me if the list is a list of linear models or a list of robust linear models. After many attempts I haven't manage to get a way to obtain which one it is.

Any suggestion please?

Answer

Reproducible example:

```
library(MASS)
fitlm <- lm(Height ~., trees)
fitrlm <- rlm(Height ~., trees)
class(fitlm)[1]
class(fitrlm)[1]
```