The following:
c( tapply( x, (row(x)-1)%/%5, mean ) ) gives a vector whose first element is the mean of every element in the rows 1 through 5 inclusive, whose second element is the mean of every element rows 6 through 10 inclusive, etc. --- Date: 4 Dec 2003 14:03:57 +0100 From: Jan Wantia <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Subject: [R] get mean of several rows Dear all! After hours of trying around, I gave up: I have a 2-dimensional array, and I know how to split it into its rows and how to get the mean for every row using 'sapply'. But what I want is to calculate the mean over the first n rows, and then the second n rows, etc., so that I get a vector like: v == mean1(row 1:5), mean2(row6:10),... (trivial, you might say. I find it rather mind-boggling, though: I tried to get the mean from the array before splitting it, after splitting it, looping through it with for-loops...I feel like an idiot by now; looks like I missed a crucial point of how 'R' works.) Thanks a lot in advance! -- ______________________________________________________ Jan Wantia Dept. of Information Technology, University of Zürich Andreasstr. 15 CH 8050 Zürich Switzerland ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help