[R] extracting a percentage of data by random

[jim holtman]

Here is one way of doing it:

> x <- data.frame(group=sample(1:4,100,TRUE), age=runif(100,4,80))
> tapply(x$age, x$group, function(z) mean(z[sample(seq_along(z), length(z) / 10)]))
       1        2        3        4
34.56628 58.70901 54.26239 58.89306
>
>


On Wed, Mar 5, 2008 at 7:49 PM, Chang Liu <changisme at hotmail.com> wrote:
>
> Hello Gurus:
>
> If I have a dataframe with one of the variables called "age" for example, and I want to extract a random 10% of the observations from each "age" group of the entire data frame. Do I have to double loop to split the data and then loop again to assign random numbers? Or is there a better way to do this?
>
> Thanks!
> Karen
>
>
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?