[R] filtering out data

Fri Aug 22 18:28:52 CEST 2008

On Fri, 22 Aug 2008, Kate Rohrbaugh wrote:

> Greetings,
>
> Apologies for such a simple question, but I have been trying to figure 
> this out for a few days now (I'm quite new to R), have read manuals, 
> list posts, etc., and not finding precisely what I need.  I am 
> accustomed to working in Stata, but I am currently working through the 
> multilevel package right now.  In Stata, I would include the statement 
> "if model1 == 1" at the end of my regression statement, but I can't seem 
> to find the correct syntax for doing the same thing in R.

You want the subset= argument to lm(), eg subset= model1==1

 	-thomas

> I have successfully converted Stata datasets, merged, aggregated, run lm, etc., but this simple task is evading me entirely.
>
> Here's what I have tried (and various iterations):
>
> if(merged.dataset$model1 == 1) model1.coeff <- lm(dv ~ iv1 + iv2 + iv3, data = merged.dataset)
> I get this:
> Warning message:
> In if (merged.dataset$model1 == 1) model1.coeff <- lm(dv ~ iv +  :
>  the condition has length > 1 and only the first element will be used
> What it seems to do is just run lm on the first opportunities of model1==1, but then doesn't try it again.  I tried sorting so that the model1==1 appear first, but that doesn't seem to be a great solution either.
>
> I'll just go back into Stata and create separate new datasets if I have to, but there HAS to be a more elegant way.
>
> Thank you for ANY feedback!
>
> Kate
>
> Kate Rohrbaugh
> Independent Project Analysis, Inc.
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>
> office - 703.726.5465
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Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle