[R] matrix operation

[Achim Zeileis]

On Fri, 07 Oct 2005 18:01:41 -0400 Dhiren DSouza wrote:

> Hello:
> 
> I have a matrix 'dat' with 2 columns.
> 
> I have the following code:
> 
> for (i in 1:nrows(dat))
> {
>   if (dat[i,1] < dat[i,2])
>     {
>       dat[i,2]<-0
>     }
> 
>    else
>    {
>      dat[i,2]<-1
>    }
> 
> Is there a way to accomplish this without the for loop?

For this setting
  dat[,2] <- as.numeric(dat[,1] >= dat[,2])
seems to work.

For more complicated tasks look at ifelse().

hth,
Z


> Thank you.
> 
> -Dhiren
> 
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