kasperdanielhansen / bpca

bpca

Cross-product

Assume single-cell data with many more columns than rows. Input is x : m (rows, fixed) x n (columns, number of cells)

Want to compute tcrossprod(x) = x %*% t(x) result has dimension m x m

m <- 500     # Total number of rows
n <- 1000    # Total number of columns
X <- DelayedArray(matrix(rnorm(m*n), ncol=n))

# Regular crossprod
system.time({
  ref <- crossprod(as.matrix(X))
})

## Test 2
# Crossprod on DelayedArray of in memory matrix
system.time({
  out <- tcrossprod1
})