R help - Sep 2014 - division of col by the sum of the col

Hi,
If I want to divide the column of a matrix by the sum of the column, should I
loop over the columns or can I use apply family?


Regards,

Carol
	[[alternative HTML version deleted]]

Neither. Unless I misjudge, you really really need to do your homework
and read some basic R documentation -- e.g. An Intro to R, which ships
with R (and also the Posting Guide) -- before posting here further.

-- Bert

Bert Gunter
Genentech Nonclinical Biostatistics
(650) 467-7374

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
Clifford Stoll




On Tue, Sep 23, 2014 at 8:10 AM, carol white <wht_crl at yahoo.com>
wrote:
> Hi,
> If I want to divide the column of a matrix by the sum of the column, should
I loop over the columns or can I use apply family?
>
>
> Regards,
>
> Carol
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> 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.

> If I want to divide the column of a matrix by the sum of the column, should
I
> loop over the columns or can I use apply family?
Looping's unnecessary.
See ?scale  or ?sweep, with  ?colSums for two non-looping answers; apply() also
works if you give it a suitable function argument.

S



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On 24/09/14 03:10, carol white wrote:
> Hi, If I want to divide the column of a matrix by the sum of the
> column, should I loop over the columns or can I use apply family?
m1 <- apply(m,2,function(x){x/sum(x)})

should do what you want IIUYC.

cheers,

Rolf Turner

-- 
Rolf Turner
Technical Editor ANZJS