[R] Get a percent variable based on group

Jeff Newmiller jdnewmil at dcn.davis.CA.us
Wed Jan 16 07:12:48 CET 2013

As others have said, your goal is unclear to us. However, one guess I have not seen others make is if you are looking for a way to normalize within each group, perhaps you should look at


which typically creates a vector just as long as your data vector and grouping vector.
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Karine Charlebois <karine.charlebois at outlook.com> wrote:

>Dear all, I'd like to get a percentage variable based on a group, but
>without creating a new data frame. 
>For example:
>iris$percent <-unlist(tapply(iris$Sepal.Length,iris$Species,function(x)
>x/sum(x, na.rm=TRUE)))
>This does not work, I should have only three standard values,
>respectively for setosa, versicolor, and virginica. How can I do this?
>	[[alternative HTML version deleted]]
>R-help at r-project.org mailing list
>PLEASE do read the posting guide
>and provide commented, minimal, self-contained, reproducible code.

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