I use the following function to select a subgroup from a data vector
(usually to calculate descriptive stats).
select.range<-function (groupvec, min, max, data)
{
if (nargs() > 3) {
min.cond <- groupvec >= min
max.cond <- groupvec < max
cond <- min.cond & max.cond
selected <- na.remove(ifelse(cond, data, NA))
invisible(selected)
}
else cat("Usage: select.range(groupvec,min,max,datavec)\n")
}
e.g.
> tdata.df<-read.table("tdata",header=T,sep=",")
> tdata.df
group value year
1 1 0 1980
2 1 10 1981
3 1 14 1982
4 1 20 1983
5 1 25 1984
6 1 30 1985
7 2 0 1980
8 2 5 1981
9 2 6 1982
10 2 8 1984
11 3 0 1984
12 3 2 1985
13 4 0 1980
14 4 20 1981
15 4 30 1982
16 4 30 1984
17 4 35 1985> value1<-select.range(tdata.df$group,1,1.1,tdata.df$value)
> value1
[1] 0 10 14 20 25 30
Note that you cannot use 1,1 as the range - you'll get an empty result.
Apologies if it's not sufficiently elegant.
Jim
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