[R] [Fwd: Excluding data with apply]

[Christian Kamenik]

Dear all,

I've got many responses to my initial question, which is stated below. 
However, from those responses it has become clear that I need to 
rephrase my problem. All responses dealt with subscripting the data 
matrix before 'apply' is run on it. But this is not want I wanted to do.
'apply' cycles through rows or columns of a matrix, and runs a function 
on each row or column individually. Now, instead of focusing on each 
individual row or column, I want to get rid of these rows or columns, 
and run the function on the remaining matrix.
I could do this with a for loop, such as:

x<-matrix(rnorm(100),20,5)
for (i in 1:ncol(x)) print(mean(x[,-i]))

But for more complex problems this becomes tedious...

Any ideas would be highly appreciated, Christian

>
> Dear all,
>
> 'Apply' is a great thing for running functions on rows or columns of a 
> matrix:
>
> X <- rnorm(20, mean = 0, sd = 1)
> dim(X) <- c(5,4)
> apply(X,2,sum)
>
> Is there a way to use apply for excluding rows or columns from a matrix 
> to run functions on the remaining rows or columns? I know, I could do 
> this with a 'for' loop, but 'apply' would be much easier and quicker, 
> and require less programming...
>
> Cheers, Christian
>   


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Oeschger Centre for Climate Change Research, Institute of Geography & Institute of Plant Sciences
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