hasimag¶

Purpose¶

Tests whether the imaginary part of a complex matrix is negligible.

Format¶

y = hasimag(x)¶

Parameters:: x (NxK matrix) – data
Returns:: y (scalar) – 1 if the imaginary part of x has any nonzero elements, 0 if it consists entirely of 0’s.

Examples¶

x = { 1   2 3i,
      4-i 5 6i,
      7   8i 9 };

if hasimag(x);
    // code path for complex case
    print "X has non-zero imaginary parts"
else;
    // code path for real case
    print "X does not have non-zero imaginary parts"
endif;

Remarks¶

The function iscplx() tests whether x is a complex matrix or not, but it does not test the contents of the imaginary part of x. hasimag() tests the contents of the imaginary part of x to see if it is zero.

hasimag() actually tests the imaginary part of x against a tolerance to determine if it is negligible. The tolerance used is the imaginary tolerance set with the sysstate() command, case 21.

Some functions are not defined for complex matrices. iscplx() can be used to determine whether a matrix has no imaginary part and so can pass through those functions. hasimag() can be used to determine whether a complex matrix has a negligible imaginary part and could thus be converted to a real matrix to pass through those functions.

iscplx() is useful as a preliminary check because for large matrices it is much faster than hasimag().