R help - Jan 2012 - Return the matrix location of multiple entries

Hello! 

I'm working with a matrix called 'subER'. This matrix has 150(=h)
rows and
15 columns. What I would like to do is have a command that will identify the
minimum 4 values in each row and return the column numbers where these
values were found. My hope is to store this information in a new 150 by 4
matrix called P. 

So far I've only been able to get R to identify one minimum value and return
its corresponding column location: 

P=matrix(nrow=h, ncol=1)
for(i in 1:h){
P[i,]=which.min(subER[i,])
}

Any help would be greatly appreciated!! 

Thank you in advance, 

Jess 


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I'd do something like

apply(subER, 1, function(x) which(x %in% sort(x)[1:4]))

E.g.

subER <- matrix(sample(100), 10)

But I'll admit that seems clunkier than it should be.

On Mon, Jan 23, 2012 at 12:41 PM, connollj <connollj at uoguelph.ca>
wrote:
> Hello!
>
> I'm working with a matrix called 'subER'. This matrix has
150(=h) rows and
> 15 columns. What I would like to do is have a command that will identify
the
> minimum 4 values in each row and return the column numbers where these
> values were found. My hope is to store this information in a new 150 by 4
> matrix called P.
>
> So far I've only been able to get R to identify one minimum value and
return
> its corresponding column location:
>
> P=matrix(nrow=h, ncol=1)
> for(i in 1:h){
> P[i,]=which.min(subER[i,])
> }
>
> Any help would be greatly appreciated!!
>
> Thank you in advance,
>
> Jess
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Return-the-matrix-location-of-multiple-entries-tp4321412p4321412.html
> Sent from the R help mailing list archive at Nabble.com.
>
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