### Testing the group methods

library(Matrix)
set.seed(2001)

mm <- Matrix(rnorm(50 * 7), nc = 7)
xpx <- crossprod(mm)# -> "factors" in mm !
round(xpx, 3) # works via "Math2"

y <- rnorm(nrow(mm))
xpy <- crossprod(mm, y)
res <- solve(xpx, xpy)
signif(res, 4) # 7 x 1 Matrix

## exp(): component wise
signif(dd <- (expm(xpx) - exp(xpx)) / 1e34, 3)# 7 x 7

stopifnot(validObject(xpx),
          validObject(xpy),
          validObject(dd))

proc.time() # for ``statistical reasons''