Get variable names from results of lm()

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
Of Marc Schwartz
Sent: Wednesday, May 23, 2012 12:13 PM
To: Peter Ehlers
Cc: r-help at r-project.org; jdub
Subject: Re: [R] Get variable names from results of lm()


On May 23, 2012, at 1:42 PM, Peter Ehlers wrote:

On 2012-05-23 09:55, R. Michael Weylandt wrote:

I think the easiest that comes to mind is simply

names(coef(myMod))

But did you look at myMod$terms[[3]] ? That seems to be the RHS of the
formula input (in the few cases I tried)

Best,
Michael

It depends a bit on just what the OP wants. In case one of the
predictors is a factor, say 'grp' with levels c('A','B','C'), the
coefs will include the names 'grpB' and 'grpC'. If only the
name 'grp' is wanted, one could use myMod$terms[[3]] or
equivalently formula(myMod)[[3]]. It might be instructive for the
OP to look at as.list(formula(myMod)). formula(myMod) is a
language object which has the tilde operator operate on
the LHS (component 2) and the RHS (component 3).

Peter Ehlers

Just to throw out another solution here, the function ?all.vars is helpful:

LM <- lm(Petal.Length ~ ., data = iris)

formula(LM)

Petal.Length ~ Sepal.Length + Sepal.Width + Petal.Width + Species

all.vars(formula(LM))

[1] "Petal.Length" "Sepal.Length" "Sepal.Width"  "Petal.Width"
[5] "Species"


Regards,

Marc Schwartz

On Wed, May 23, 2012 at 10:58 AM, jdub<jack at ramas.com>  wrote:

What is the best way to get the variable names used in lm() from its
results?

Stumbling around I found I could get the response variable name from

myMod$terms[[2]]

but using

myMod$terms[[1 ]]

gives a tilda.

I found the names buried in other places in the model object and in the
summary of the model, but is there a more direct way, similar to using
coef(myMod) to get the coefficients?