> Hi All,
>
> I'm conducting a meta-analysis and have taken a data.frame with multiple
> rows per
> study (for each effect size) and performed a weighted average of effect
> size for
> each study. This results in a reduced # of rows. I am particularly
> interested in
> simply reducing the additional variables in the data.frame to the first row
> of the
> corresponding id variable. For example:
>
> id<-c(1,2,2,3,3,3)
> es<-c(.3,.1,.3,.1,.2,.3)
> mod1<-c(2,4,4,1,1,1)
> mod2<-c("wai","other","calpas","wai","itas","other")
> data<-as.data.frame(cbind(id,es,mod1,mod2))
>
> data
>
>    id   es    mod1 mod2
> 1  1   0.3    2     wai
> 2  2   0.1    4     other
> 3  2   0.2    4     calpas
> 4  3   0.1    1     itas
> 5  3   0.2    1     wai
> 6  3   0.3    1     wai
>
> # I would like to reduce the entire data.frame like this:
>
> id  es   mod1  mod2
>
> 1  .30     2        wai
> 2  .15     4        other
> 3  .20     1         itas
>
> # If possible, I would also like the option of this (collapsing on id and
> mod2):
>
> id  es   mod1  mod2
> 1  .30      2        wai
> 2   0.1     4       other
> 2   0.2      4        calpas
> 3   0.1     1         itas
> 3   0.25    1         wai
>
> Any help is much appreciated!
>
> AC Del Re
>

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