[R] variable number of variables in data frames

[Robert.Denham@dnr.qld.gov.au]

> For example, if I know columns 1:4 are to be treated as factors, I can
> write

> dat <- matrix(c(2,1,1,1, 1,1,1,1), 2, 4)
> D <- as.data.frame(dat)


> # force all variables to be treated as binary
>.# regardless of the small data set
> D$V1 <- factor(D$V1, 1:2)
> D$V2 <- factor(D$V2, 1:2)
> D$V3 <- factor(D$V3, 1:2)
> D$V4 <- factor(D$V4, 1:2)

> But how do I do this in general? What I would like to say is something
> like

Why not just 
for (i in my.factor.columns) {
#  D$Vi <- factor(D$Vi, 1:my.nlevels[i])
   D[,i]<- factor(D[,i], 1:my.nlevels[i])
}

Robert


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