On 06/21/2011 09:48 AM, davefrederick wrote:
Hi, I have a 500x 53380 sparse matrix and I am trying to dichotomize it.
Under sna package I have found event2dichot yet it doesnt recognize sparse
matrix and requires adjacency matrix or array. I tried to run a simple loop
code
for (i in 1:500)
for (j in 1:53380)
if (matrix[i,j]>0) matrix[i,j]=1
The code you are running does not require a loop:
> A <- cbind(c(1,0),c(0,2))
> A
[,1] [,2]
[1,] 1 0
[2,] 0 2
> A[A>0] <- 1
> A
[,1] [,2]
[1,] 1 0
[2,] 0 1
However, for large sparse matrices, this and other operations will be
faster if the matrix is explicitly stored as a sparse matrix, as
implemented in the 'Matrix' package.
--
Patrick Breheny
Assistant Professor
Department of Biostatistics
Department of Statistics
University of Kentucky
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