yes, exactly!  Thanks a lot for your quick answer :)

jim holtman <jholtman@gmail.com> wrote: Is this what you want?

> x <- matrix(1:25,5)
> x[c(2,5),5] <- -9999
> x
     [,1] [,2] [,3] [,4]  [,5]
[1,]    1    6   11   16    21
[2,]    2    7   12   17 -9999
[3,]    3    8   13   18    23
[4,]    4    9   14   19    24
[5,]    5   10   15   20 -9999
> x[x[,5] == -9999, 5] <- NA
> x
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    6   11   16   21
[2,]    2    7   12   17   NA
[3,]    3    8   13   18   23
[4,]    4    9   14   19   24
[5,]    5   10   15   20   NA
>
>


On 9/29/06, bertrand toupin  wrote:
> Hi!  1st time I'm posting here.  I'm beginning to learn R and I've encountered a problem that I'm unable to solve so far.
>
> I have  a 20 000 x 5 matrix.  In the 5th column, I have elevation.  Missing value are actually put to -99999.  I want to track down the index of those values and replace them with NA.  I've read that to replace, the command "replace" is enough.  I just don't know how to construct the index vector that contains the index of -99999 values.
>
> Hope this makes sense,
> Thanks!
> Philippe
>
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?


 				
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