[R] newbie question: ROW average
Rolf Turner
rolf at math.unb.ca
Mon May 29 13:55:50 CEST 2006
Dimitris Rizopoulos wrote:
> look at ?rowMeans; you can also use "apply(mat, 1, mean)" but
> rowMeans() is better.
By my reading of the question, this is not what
Ezhil wants. He said:
``I have a 992 x 74 matrix. I would like to form a new matrix
by averaging each 4 rows from the original one.''
I.e. he wants (I think) the first row of the new matrix
to be the mean of the first 4 rows of the old one, the
second row of the new matrix to be the mean of rows 5
through 8 of the old one, and so on.
One way this could be done is via
> m.new <- t(apply(array(t(m.old),dim=c(74,4,992/4)),c(1,3),mean))
cheers,
Rolf Turner
rolf at math.unb.ca
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