Change to array indicies to prevent overflow.

[gumeo]

Hi

This is a small contribution which is a fix to a problem I ran into.

I had an issue with the SKAT package on TTN with 500K rows and 10K columns. The index returned from the which function can exceed the maximum length of an underlying C array, resulting in an overflow. Using array indices fixes this problem.

Best regards,
Guðmundur Einarsson

[gumeo]

Hi again,

Here is a simple example to illustrate the problem:

library(Matrix)

# Create an empty sparse matrix
m <- Matrix(0, nrow = 500000, ncol = 10000, sparse = TRUE)

# Set one element to 10 at a high index position
m[5, 6000] <- 10

# Index error:
ind <- which(m == 10)
m[ind] <- 5

# Fix:
ind <- which(m == 10, arr.ind = TRUE)
m[ind] <- 5