R help - Nov 2012 - Multiple Vector with matrix in R

Hi

Can someone show me an easy way to multiple a weighted vector with an
matrix?

example below
mat1<-matrix(sample(1:100,80,replace=TRUE),ncol=8)
w <- 1/1:10

I want the first element in w to be multiplied by the first row of mat1 and
2nd element in w to be multiplied with the 2nd row and so on.

I have huge matrix is there an easy way other than diag(w)%*%mat1

Thanks



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Hi A.K

Here is the error I get when I use %*%
> dim(X)
[1] 71142   219
> length(Weights)
[1] 71142
> Wx<-diag(Weights)%*%X
Error in array(0, c(n, p)) : 'dim' specifies too large an array

That is why I asked for different and faster method



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Hi 

No i didn't get error it executed too fast, I had question about the Sum
squares in the weighted least square if u can help me I would I appreciated

Thanks 

Date: Fri, 16 Nov 2012 09:46:59 -0800
From: ml-node+s789695n4649775h76@n4.nabble.com
To: frespider@hotmail.com
Subject: Re: Multiple Vector with  matrix in R



	HI,

Did you got the same error with sweep()?

A.K.

	
	
	
	

	

	
	
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Hello,

Try the following.

t(sapply(seq_along(w), function(i) mat1[i,]*w[i]))

Hope this helps,

Rui Barradas
Em 16-11-2012 16:34, frespider escreveu:
> Hi
>
> Can someone show me an easy way to multiple a weighted vector with an
> matrix?
>
> example below
> mat1<-matrix(sample(1:100,80,replace=TRUE),ncol=8)
> w <- 1/1:10
>
> I want the first element in w to be multiplied by the first row of mat1 and
> 2nd element in w to be multiplied with the 2nd row and so on.
>
> I have huge matrix is there an easy way other than diag(w)%*%mat1
>
> Thanks
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Multiple-Vector-with-matrix-in-R-tp4649764.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

On Nov 16, 2012, at 8:34 AM, frespider wrote:
> Hi
> 
> Can someone show me an easy way to multiple a weighted vector with an
> matrix?
> 
> example below
> mat1<-matrix(sample(1:100,80,replace=TRUE),ncol=8)
> w <- 1/1:10
> 
> I want the first element in w to be multiplied by the first row of mat1 and
> 2nd element in w to be multiplied with the 2nd row and so on.
> 
> I have huge matrix is there an easy way other than diag(w)%*%mat1
Because of argument recycling, this would be the most simple way:

mat1 * w
> mat1 * w == diag(w) %*% mat1
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
 [1,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
 [2,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
 [3,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
 [4,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
 [5,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
 [6,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
 [7,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
 [8,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
 [9,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
[10,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE


--
David Winsemius, MD
Alameda, CA, USA