[R] median of binned values
ccleland at optonline.net
Wed Dec 19 12:47:59 CET 2007
Martin Tomko wrote:
> Thank you, Chuck,
> would you mind commenting a bit on the code, it is not all clear... HOw
> would you go to retrieve only the numeric value (not the category name)?
> I am just starting with R, and the functionality of replicate and levels
> is not quite clear. I tried the documentation, but am not any wiser.
> What if I had a vector v <- vector(c(1,10,100,1000,10000)) and wanted to
> perform it on that?
> Thanks a lot
Retrieve the numeric value rather than the category name as follows:
with(df, freq[median(rep(as.numeric(binname), freq))])
To do essentially the same thing with a vector:
myvec <- c(1,10,100,1000,10000)
I'm sure I cannot explain levels() and rep() any better than the help
pages for those functions.
> Chuck Cleland wrote:
>> 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,:
>>> 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))
>> 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))])
>>  "cat5"
>>> Thanks a lot
>>> R-help at r-project.org mailing list
>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
Chuck Cleland, Ph.D.
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