[R] Averaging over columns

[Jacques VESLOT]

t(as.matrix(aggregate(t(as.matrix(DF)), rep(1:12,each=3), mean)[,-1]))




michael watson (IAH-C) a écrit :

>Hi
>
>I've been reading the help for by and aggregate but can't get my head
>round how to do this.  
>
>I have a data frame - the first three columns are replicate
>measurements, then the next 3 are replicates etc up to 36 (so 12
>variables with 3 replicate measurements each).  I want to compute the
>mean for each of the 12 variables, so that, for each row, I have 12
>means.
>
>A grouping variable across columns can easily be created by
>rep(1:12,each=3), but I can't figure out which function to use to get R
>to calculate the means I want.
>
>Thanks in advance
>Mick
>
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