[R] Help wit matrices

[jim holtman]

Is this what you want:

> x <- matrix(runif(100), 10)
> round(x, 3)
       [,1]  [,2]  [,3]  [,4]  [,5]  [,6]  [,7]  [,8]  [,9] [,10]
 [1,] 0.268 0.961 0.262 0.347 0.306 0.762 0.524 0.062 0.028 0.226
 [2,] 0.219 0.100 0.165 0.131 0.578 0.933 0.317 0.109 0.527 0.131
 [3,] 0.517 0.763 0.322 0.374 0.910 0.471 0.278 0.382 0.880 0.982
 [4,] 0.269 0.948 0.510 0.631 0.143 0.604 0.788 0.169 0.373 0.327
 [5,] 0.181 0.819 0.924 0.390 0.415 0.485 0.702 0.299 0.048 0.507
 [6,] 0.519 0.308 0.511 0.690 0.211 0.109 0.165 0.192 0.139 0.681
 [7,] 0.563 0.650 0.258 0.689 0.429 0.248 0.064 0.257 0.321 0.099
 [8,] 0.129 0.953 0.046 0.555 0.133 0.499 0.755 0.181 0.155 0.119
 [9,] 0.256 0.954 0.418 0.430 0.460 0.373 0.620 0.477 0.132 0.050
[10,] 0.718 0.340 0.854 0.453 0.943 0.935 0.170 0.771 0.221 0.929
> ifelse(x > .5, 1, 0)
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    0    1    0    0    0    1    1    0    0     0
 [2,]    0    0    0    0    1    1    0    0    1     0
 [3,]    1    1    0    0    1    0    0    0    1     1
 [4,]    0    1    1    1    0    1    1    0    0     0
 [5,]    0    1    1    0    0    0    1    0    0     1
 [6,]    1    0    1    1    0    0    0    0    0     1
 [7,]    1    1    0    1    0    0    0    0    0     0
 [8,]    0    1    0    1    0    0    1    0    0     0
 [9,]    0    1    0    0    0    0    1    0    0     0
[10,]    1    0    1    0    1    1    0    1    0     1


On 8/10/07, Lanre Okusanya <lanre.okusanya at gmail.com> wrote:
> Hello all,
>
> I am working with a 1000x1000 matrix, and I would like to return a
> 1000x1000 matrix that tells me which value in the matrix is greater
> than a theshold value (1 or 0 indicator).
> i have tried
>  mat2<-as.matrix(as.numeric(mat1>0.25))
> but that returns a 1:100000 matrix.
> I have also tried for loops, but they are grossly inefficient.
>
> THanks for all your help in advance.
>
> Lanre
>
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>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?