method <- match.arg(method, c("pairwise", "percentage"))
if (!pairwise.deletion) {
## delete the columns with at least one NA:
del <- apply(x, 2, function(xx) any(is.na(xx)))
method <- match.arg(method, c("pairwise", "percentage"))
if (!pairwise.deletion) {
## delete the columns with at least one NA:
del <- apply(x, 2, function(xx) any(is.na(xx)))