See ?sweep
sweep(a, 2, a[1,],"/")
-Christos
-----Original Message-----
From: r-help-bounces@(protected)
[mailto:r-help-bounces@(protected)
toby_marks@(protected)
Sent: Wednesday, September 06, 2006 11:49 AM
To: r-help@(protected)
Subject: [R] Matrix multiplication using apply() or lappy() ?
I am trying to divide the columns of a matrix by the first row in the
matrix.
I have tried to get this using apply and I seem to be missing a concept
regarding the apply w/o calling a function but rather command args %*% /
etc. Would using apply be more efficient than this approach?
I have observed examples in the archives using this type of approach. Does
anybody have a snippet of a call to apply() that would accomplish this as
well?
Thanks!
seed=50
$a = array(rnorm(20),dim=c(4,5))
$b = matrix(a[1,],dim(a)[1],dim(a)[2],byrow=T)
$a
[,1] [,2] [,3] [,4] [,5]
[1,] -1.3682810 -0.4314462 1.57572752 0.67928882 -0.3672346 [2,] 0.4328180
0.6556479 0.64289931 0.08983289 0.1852306 [3,] -0.8113932 0.3219253
0.08976065 -2.99309008 0.5818237 [4,] 1.4441013 -0.7838389 0.27655075
0.28488295 1.3997368
$a/b
[,1] [,2] [,3] [,4] [,5]
[1,] 1.0000000 1.0000000 1.00000000 1.0000000 1.000000 [2,] -0.3163225
-1.5196515 0.40800157 0.1322455 -0.504393 [3,] 0.5930018 -0.7461539
0.05696457 -4.4062113 -1.584338 [4,] -1.0554128 1.8167710 0.17550671
0.4193841 -3.811560
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
