Re: [R] Problem using apply

From: Joachim de Lezardiere <joachim.lezard_at_gmail.com>
Date: Tue, 01 Jun 2010 21:21:18 +0200

Thank you Henrique,  

I still don’t understand why my code doesn’t work ? According to the definition of apply function it should work no ?  

From: Henrique Dallazuanna [mailto:wwwhsd_at_gmail.com] Sent: Tuesday, June 01, 2010 7:34 PM
To: Joachim de Lezardiere
Cc: r-help_at_r-project.org
Subject: Re: [R] Problem using apply  

The mean by col and by row are the same:

colMeans(m) == rowMeans(m)

So:

m / rowMeans(m) # You don't need apply here m / colMeans(m)

On Tue, Jun 1, 2010 at 2:26 PM, Joachim de Lezardiere <joachim.lezard_at_gmail.com> wrote:

Hello ,

I can not get apply function to do what I want when doing stuff on rows. Let's say I want to divide the rows of matrix by their mean, the below show you get the same result weather you use 1 or 2, i.e. same result for columns than for means..:(

Thanks a lot for the help,

m = matrix( c(1,4,7,4,5,8,7,8,9), nrow = 3 )

divideByMean = function( v ){

return( v/mean(v))

}

rowMean = c( mean( m[1,]),mean( m[2,]),mean( m[3,]) )

rowMean

colMean = c( mean( m[,1]),mean( m[,2]),mean( m[,3]) )

colMean

m

print("ByRow")

apply( m, 1, divideByMean)

print("ByCol")

apply( m, 2, divideByMean)

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Henrique Dallazuanna
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