Matrices with randomly generated entries

I'm attempting to generate matrices where the entries are randomly generated
numbers of specified distribution.

The following code was an attempt to create a 3 by 3 matrix, where my
entries where randomly generated from a uniform (0,1) distribution.

x = matrix(0,ncol = 3, byrow = T)
for(i in 1:3) {
 for(j in 1:3) { x[i,j]= runif(1,0,1) }
}

The problem I get with the above code however is that I get an error message
which says the following;

"Error in x[i,j]= runif(1,0,1)  :   subscript out of bounds"

I haven't been able to figure out how to fix this. Any help would be much
appreciated.

jshort