Hi,
I want to select a subsample from my data, choosing one record from each
group. I know how to do this with a for.
For example: lets say I have the data:
A=cbind(rnorm(100),runif(100),(rep(c(1,2,3,4,5),20)))
Where the third column is the group variable. Then what I want is to select
5 observations. Each one taken randomly from each group.
INDEX =NULL
i=1
for(index_g in unique(A[,3])){
INDEX [i]=sample(which(A[,3]==index_g),1)
i=i+1
}
SEL=A[INDEX,]
Is there a way to do this without a for? in other words is there a way to
vectorize this?
Thank you,
Mauricio Romero
Quantil S.A.S.
Bogotá,Colombia
www.quantil.com.co
"It is from the earth that we must find our substance; it is on the earth
that we must find solutions to the problems that promise to destroy all life
here"
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