[R] subset

[Vaidotas Zemlys]

Hi,

> I have a simple question. If I need to run linear regression on a subset of
> the dataset, will
> the following two commands give the same output:
> 
> lm(y ~ as.factor(x1) + as.factor(x2), data, subset = z==Z[1])
> 
> and
> 
> lm(y ~ as.factor(x1) + as.factor(x2), data[data$z==Z[1],] )
> 
> 
> I have got different results running the two commands. Am I missing
> something here, or it
> there a bug on the option subset?
> 

I tried the same thing  at my computer and everything works fine. Maybe 
you have variable z, which is not the same as in your data frame. That is

data$z!=z,

Try do something like

zz_z
rm(z)

and then repeat your two lm calls. Then I think the results should be 
the same.

Vaidotas Zemlys

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