R help - Nov 2010 - how to divide each column in a matrix by its colSums?

Hi,

I have a matrix, say 
m=matrix(c(
	983,679,134,
	383,416,84,
	2892,2625,570
	),nrow=3
)

i can find its row/col sum by

rowSums(m)
colSums(m)

How do I divide each row/column by its rowSum/colSums and still return in
the matrix form?
(i.e. the new rowSums/colSums =1)

Thanks.

Casper

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Hi Casper,

Try

m/colSums(m)
m/rowSums(m)

HTH,
Jorge

On Sun, Nov 28, 2010 at 3:46 PM, casperyc <> wrote:
>
> Hi,
>
> I have a matrix, say
> m=matrix(c(
>        983,679,134,
>        383,416,84,
>        2892,2625,570
>        ),nrow=3
> )
>
> i can find its row/col sum by
>
> rowSums(m)
> colSums(m)
>
> How do I divide each row/column by its rowSum/colSums and still return in
> the matrix form?
> (i.e. the new rowSums/colSums =1)
>
> Thanks.
>
> Casper
>
> --
> View this message in context:
>
http://r.789695.n4.nabble.com/how-to-divide-each-column-in-a-matrix-by-its-colSums-tp3062739p3062739.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@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.
>
	[[alternative HTML version deleted]]

In that case, there are values >1,
which is clearly not what I wanted.

Thanks.

I think I should use prop.table


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prop.table divides every element by the matrix total, not its colSums:

 > m <- matrix(1:4, 2)
 > m
      [,1] [,2]
[1,]    1    3
[2,]    2    4
 > prop.table(m)
      [,1] [,2]
[1,]  0.1  0.3
[2,]  0.2  0.4


       m/rowSums(m) divides every row by its rowSum:

 > m/rowSums(m)
           [,1]      [,2]
[1,] 0.2500000 0.7500000
[2,] 0.3333333 0.6666667


       To divide every element by its colSum:


 > t(t(m)/rowSums(t(m)))
           [,1]      [,2]
[1,] 0.3333333 0.4285714
[2,] 0.6666667 0.5714286


       Hope this helps.
       Spencer


On 11/28/2010 12:55 PM, casperyc wrote:
> In that case, there are values>1,
> which is clearly not what I wanted.
>
> Thanks.
>
> I think I should use prop.table

sweep(m,1,rowSums(m),"/")
sweep(m,2,colSums(m),"/")




On 11/28/2010 9:55 PM, casperyc wrote:
> 
> In that case, there are values >1,
> which is clearly not what I wanted.
> 
> Thanks.
> 
> I think I should use prop.table
> 
>