David Winsemius wrote:
>
>
> ...
>
> Perhaps:
>
> by(data2, data2$grp, function(x) step(lm(model, data=x)))
>
>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>
>
Perhaps ;) You know of course that this worked. It took a moment to
understand the screen output bec
Dieter Menne wrote:
>
> ...
>
> Looks like an environment problem. I could not find a workaround quickly,
> but you might have a look at
>
> http://finzi.psych.upenn.edu/R/Rhelp02a/archive/16599.html
>
> We call it "Ripley's Game" here, because variants of it can help you quite
> often.
>
On Jun 22, 2009, at 4:08 AM, Dieter Menne wrote:
Chris Friedl gmail.com> writes:
I have two questions about the built-in function step. Ultimately I
want to
apply a lm fitting and subsequent step procedure to thousands of
data sets
groups by a factor defined as a unique ID.
Q1. The code
Chris Friedl gmail.com> writes:
> I have two questions about the built-in function step. Ultimately I want to
> apply a lm fitting and subsequent step procedure to thousands of data sets
> groups by a factor defined as a unique ID.
>
> Q1. The code below creates a data.frame comprising three mar
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