examples/example-tcrossprodSelf.R

In privefl/bigstatsr: Statistical Tools for Filebacked Big Matrices

X <- FBM(13, 17, init = rnorm(221))
true <- tcrossprod(X[])

# No scaling
K1 <- tcrossprod(X)
class(K1)
all.equal(K1, true)

K2 <- big_tcrossprodSelf(X)
class(K2)
K2$backingfile
all.equal(K2[], true)

# big_tcrossprodSelf() provides some scaling and subsetting
# Example using only half of the data:
n <- nrow(X)
ind <- sort(sample(n, n/2))
K3 <- big_tcrossprodSelf(X, fun.scaling = big_scale(), ind.row = ind)
true2 <- tcrossprod(scale(X[ind, ]))
all.equal(K3[], true2)