[R] *apply function for arrays?

From: Hesen Peng <hesen.peng_at_gmail.com>
Date: Sun, 18 May 2008 09:57:00 +0800


Hi all,

I've recently been writing functions which may deal with very large arrays. And I hope to use *apply functions in the program so that the code may look nicer and the performance may be better in the following two situations.

The first situation is:

I'm having an array A with dim(A)==c(m,n,p). And I want to apply a function F to a group of elements in A like:

  1. F is applied to every group of elements like A[i,j,] for all i and j. or
  2. F is applied to every group of elements like A[i,,] for all i, or A[,j,] for all j.

The result is then expected to be a m*n-dimensional matrix

I'm currently using for loops to do this but I guess there maybe some *apply functions for arrays which may accomplish this task.

The second situation is:

I'm having two matrix M and N and a function G, which is a function of two arrays. I want to form a matrix R with dim(R)==c(nrow(M),nrow(N)), and R[i,j] <- G(M[i,], N[j,]). And I wonder whether I may use some functions like outer to the matrix.

Thank you very much and have a nice weekend.

-- 
彭河森 Hesen Peng
http://hesen.peng.googlepages.com/
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Received on Sun 18 May 2008 - 01:59:42 GMT

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