[R] transforming column of a dataframe by var- and median-functions

[Daniel Malter]

I think tapply does the job you want:

tapply(C,B,mean,na.rm=TRUE)
tapply(C,B,var,na.rm=TRUE)

Cheers,
Daniel

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Von: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] Im
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Gesendet: Sunday, March 09, 2008 4:38 PM
An: R-help at r-project.org
Betreff: [R] transforming column of a dataframe by var- and median-functions

Hello,

I try to transform a data frame like

A        B        C

1        1        2,5
2        2        NA
3        1        1,0
4        1        56
5        2        23
6        1        NA
7        2        46

to the following dataframe, calculating the variance and median of the
C-column, group by B, so the result will be:

B        C(median)         D (var)
1        19,83                9
2        34,5                21


Doing this, I got problems with the NAs in column C.
I tried to combine the aggregate - function aggregate(C, list(B), FUN=(mean,
var))

with the following functions

var(C, use="complete.obs")
median(C, rm.na=TRUE)

but it doesn't work as I want. Has anybody an idea how to do this work?

thank you
Iksmax

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