R help - Oct 2005 - matrix operation

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?

Thank you.

-Dhiren

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
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>

There a re a few ways to do it without loop. Here is one:
 
 dat = matrix(runif(100), 50,2)
 dat[,1] = dat[,1] >= dat[,2]

 Jarek 
====================================================\==== 
 Jarek Tuszynski, PhD.                           o / \ 
 Science Applications International Corporation  <\__,|  
 (703) 676-4192                                   ">  \ 
 Jaroslaw.W.Tuszynski at saic.com                     `   \ 



-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] 
Sent: Friday, October 07, 2005 6:02 PM
To: r-help at stat.math.ethz.ch
Subject: [R] matrix operation

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?

Thank you.

-Dhiren

______________________________________________
R-help at stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html