.117015
>
> --
> David L. Carlson
> Department of Anthropology
> Texas A&M University
>
> -Original Message-
> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Jim Lemon
> Sent: Saturday, April 2, 2016 6:14 PM
> To: Pedro Mar
2016 6:14 PM
To: Pedro Mardones
Cc: r-help mailing list
Subject: Re: [R] apply mean function to a subset of data
Hi Pedro,
This may not be much of an improvement, but it was a challenge.
selvec<-as.vector(matrix(c(nsel,unlist(by(toy$diam,toy$group,length))-nsel),
ncol=2,byrow=TRUE))
TFv
Hi Pedro,
This may not be much of an improvement, but it was a challenge.
selvec<-as.vector(matrix(c(nsel,unlist(by(toy$diam,toy$group,length))-nsel),
ncol=2,byrow=TRUE))
TFvec<-rep(c(TRUE,FALSE),length.out=length(selvec))
toynsel<-rep(TFvec,selvec)
by(toy[toynsel,]$diam,toy[toynsel,]$group,mean)
Your toy code does not reproduce what you describe: mean(toy$diam[1:nsel[i]])
both times selects from elements of group 1. YOu probably want to subset like
toy$diam[toy$group == i]. Also, if there is any real inefficiency here, it is
_not_ because you are executing a for-loop for two iterations.
Dear all;
This must have a rather simple answer but haven't been able to figure it
out: I have a data frame with say 2 groups (group 1 & 2). I want to select
from group 1 say "n" rows and calculate the mean; then select "m" rows from
group 2 and calculate the mean as well. So far I've been using a
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