[R] R syntaxe

[Martin Olivier]

Hi all,

Suppose I have a vector x with numerical values.
In y, I have a categorial variable : y<-c(1,1,..2,2,...30,30,30)
x and y have the same length.
I would like to compute the mean for x for the modality 1 to 30 in y.
mean(x[y==1]),...,mean(x[y==30])
I do not want to use an iterative procedure such that for (i in 1:30)..
Thanks for your help,

Regards.
Olivier.


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Martin Olivier
INRA - Unité Biostatistique & Processus Spatiaux
Domaine St Paul, Site Agroparc
84914 Avignon Cedex 9, France
Tel : 04 32 72 21 57