[R] Odp: question about "mean"

[Petr PIKAL]

Hi

split/sapply can be used besides other options

sapply(split(iris[,1:4], iris$Species), mean)

Regards
Petr

r-help-bounces at r-project.org napsal dne 10.06.2010 00:43:29:

> Hi there:
>      I have a question about generating mean value of a data.frame. Take
> iris data for example, if I have a data.frame looking like the 
following:
> ---------------------
>     Sepal.Length Sepal.Width Petal.Length Petal.Width    Species
> 1                    5.1               3.5                  1.4
>     0.2     setosa
> 2                    4.9               3.0                  1.4
>     0.2     setosa
> 3                    4.7               3.2                   1.3
>    0.2     setosa
> .                         .                   .                      .
>              .              .
> .                         .                   .                      .
>             .               .
> .                         .                   .                      .
>             .               .
> -----------------------
> There are three different species in this table. I want to make a table 
and
> calculate mean value for each specie as the following table:
> 
> -----------------
>                              Sepal.Length Sepal.Width Petal.Length
> Petal.Width
> mean.setosa                    5.006            3.428             1.462
>       0.246
> mean.versicolor               5.936             2.770             4.260
>       1.326
> mean.virginica                  6.588            2.974             5.552
>       2.026
> -----------------
> Is there any short syntax can do it?? I mean shorter than the code I 
wrote
> as following:
> 
> attach(iris)
> mean.setosa<-mean(iris[Species=="setosa", 1:4])
> mean.versicolor<-mean(iris[Species=="versicolor", 1:4])
> mean.virginica<-mean(iris[Species=="virginica", 1:4])
> data.mean<-rbind(mean.setosa, mean.versicolor, mean.virginica)
> detach(iris)
> ------------------
> 
> Thanks a million!!!
> 
> 
> -- 
> =====================================
> Shih-Hsiung, Chou
> System Administrator / PH.D Student at
> Department of Industrial Manufacturing
> and Systems Engineering
> Kansas State University
> 
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> 
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