[R] using lm() with variable formula [Broadcast]
Liaw, Andy
andy_liaw at merck.com
Fri May 18 12:50:38 CEST 2007
One way to do it is by giving a data frame with the right variables to
lm() as the first argument each time. If lm() is given a data frame as
the first argument, it will treat the first variable as the LHS and the
rest as the RHS of the formula.
As examples, you can do:
lm(myData[c("height", "weight", "BP", "Cals")])
(The drawback to this is that the "formula" in the fitted model object
looks a bit strange...)
Andy
From: Chris Elsaesser
>
> New to R; please excuse me if this is a dumb question. I
> tried to RTFM;
> didn't help.
>
> I want to do a series of regressions over the columns in a data.frame,
> systematically varying the response variable and the the
> terms; and not
> necessarily including all the non-response columns. In my case, the
> columns are time series. I don't know if that makes a difference; it
> does mean I have to call lag() to offset non-response terms. I can not
> assume a specific number of columns in the data.frame; might
> be 3, might
> be 20.
>
> My central problem is that the formula given to lm() is different each
> time. For example, say a data.frame had columns with the following
> headings: height, weight, BP (blood pressure), and Cals
> (calorie intake
> per time frame). In that case, I'd need something like the following:
>
> lm(height ~ weight + BP + Cals)
> lm(height ~ weight + BP)
> lm(height ~ weight + Cals)
> lm(height ~ BP + Cals)
> lm(weight ~ height + BP)
> lm(weight ~ height + Cals)
> etc.
>
> In general, I'll have to read the header to get the argument labels.
>
> Do I have to write several functions, each taking a different
> number of
> arguments? I'd like to construct a string or list representing the
> varialbes in the formula and apply lm(), so to say [I'm mainly a Lisp
> programmer where that part would be very simple. Anyone have
> a Lisp API
> for R? :-}]
>
> Thanks,
> chris
>
> Chris Elsaesser, PhD
> Principal Scientist, Machine Learning
> SPADAC Inc.
> 7921 Jones Branch Dr. Suite 600
> McLean, VA 22102
>
> 703.371.7301 (m)
> 703.637.9421 (o)
>
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