[R] subsetting question

[Ivan Calandra]

Hi,

What about using functions like aggregate()?
Something like:
aggregate(Weight~datums, data=dataset1, FUN=mean)

If you need to do more things, you can create your own function for 'FUN'

HTH,
Ivan

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Ivan Calandra, ATER
University of Reims Champagne-Ardenne
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Le 20/05/15 12:03, Dieter Anseeuw a écrit :
> Dear all,
> I would like to do multiple actions on a subset of my data. Therefore, I want to create a for loop on the variable "Date" (actually a double for loop on yet another variable, but let's omit that for a moment).
> I want to run down every level of "Date" and perform multiple actions on the data from a certain date. Here is my code:
>
> for (i in 1:length(datums)){
> meanweight<-mean(dataset1[dataset1$Date==datums[i],]$Weight)
> ...
>
> However, this subsetting obviously doesn't work. How can I adjust my code so that R runs down all levels of Data in a for loop?
> (I need the for loop, not tapply(), sapply(), ...)
>
> Thanks in advance,
> Dieter Anseeuw
>
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