[R] Fw: Do GLM by groups

[Benilton Carvalho]

Check the following example for by():

      require(stats)
      attach(warpbreaks)
      by(warpbreaks, tension, function(x) lm(breaks ~ wool, data = x))

or just type:
example(by)

b


On Jul 19, 2007, at 1:18 PM, Hongmei Jia wrote:

>
> Dear All,
>
> I'm trying to do 'glm' analysis by groups just like in SAS you use "by
> variable".   I don't know how to do it in R, anyone can help with  
> this?
> i.e.
>
> group    line  rep  value
> 1              1       1       0.2
> 1              1       2       0.3
> 1     1       3       0.23
> 1             2       1       0.2
> 1             2       2       0.3
> 1             2      3       0.23
> 2              1       1       0.2
> 2              1       2       0.3
> 2     1       3       0.23
> 2             2       1       0.2
> 2             2       2       0.3
> 2             2      3       0.23
>
> in SAS we say:
> model value=line rep;
> by group;
>
> How can I do this in R?
>
> Thanks,
>
> Hongmei Jia
>
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