Matvec Users’ Guide

46 CHAPTER 7. USER-DEFINED FUNCTION
{
}
#
# Return 1, if element >= 0
# Return 0, if element == 0
# Return -1, if element < 0
#
# Tianlin Wang at UIUC, Fri Dec 30 16:10:38 CST 1994
#
local(i, j, retval);
if (A.class() == "Scalar") {
if (A > 0) retval = 1; endif;
if (A == 0) retval = 0; endif;
if (A < 0) retval = -1; endif;
}
else if (A.class() == "Vector") {
retval = Vector();
retval.resize(A.size());
for (i in 1:A.size()) {
if (A(i) > 0) retval(i) = 1; endif;
if (A(i) == 0) retval(i) = 0; endif;
if (A(i) < 0) retval(i) = -1; endif;
}
}
else if (A.class() == "Matrix") {
retval = Matrix(A.nrow(),A.ncol());
for (i in 1:A.nrow()) {
for (j in 1:A.ncol()) {
if (A(i,j) > 0) retval(i,j) = 1; endif;
if (A(i,j) == 0) retval(i,j) = 0; endif;
if (A(i,j) < 0) retval(i,j) = -1; endif;
}
}
}
else {
retval = 0;
error("sign only works for numeric objects");
}
return retval;