[R] median of binned values

[Chuck Cleland]

Martin Tomko wrote:
> Dear list,
> I have a vector (array, table row, whatever is best) of frequency values 
> for categories (or bins), and I need to find the median category. 
> Trivial to do by hand, but I was wondering if there is a means to  do it 
> in R in an elegant way.
> 
> The obvious medioan(vector) returns the median frequency for the binns, 
> and that is not what I want. i.e,:
>              freq
> cat1    1
> cat2   10  
> cat3   100  
> cat4   1000
> cat5   10000
> 
> I want it to return cat5, instead of cat3.

df <- data.frame(binname = as.factor(paste("cat", 1:5, sep="")),
                 freq = c(1,10,100,1000,10000))

df
  binname  freq
1    cat1     1
2    cat2    10
3    cat3   100
4    cat4  1000
5    cat5 10000

with(df, levels(binname)[median(rep(as.numeric(binname), freq))])
[1] "cat5"

> Thanks a lot
> Martin
> 
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Chuck Cleland, Ph.D.
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