[R] filtering out data

Fri Aug 22 17:07:10 CEST 2008

Exactly what do you want this statement to do:

if(merged.dataset$model1 == 1) model1.coeff <- lm(dv ~ iv1 + iv2 +
iv3, data = merged.dataset)

The result in the "if" is a vector of logical values (assuming that
merged.dataset is longer than 1); that is the source of the error
message.  Do you want the regression to be done on every row?  So what
is the problem you are trying to solve?

On Fri, Aug 22, 2008 at 10:47 AM, Kate Rohrbaugh
<krohrbaugh at ipaglobal.com> 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.
>
> 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.
> 44426 Atwater Drive
> Ashburn, VA  20147
>
> office - 703.726.5465
> fax - 703.729.8301
> email - krohrbaugh at ipaglobal.com
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>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?