Works fine for me.
a=orth(randn(100,12)+1i*randn(100,12));
Note that I added a call to orth.
whos a
Name Size Bytes Class Attributes
a 100x12 19200 double complex
So a is 100x12, complex, an orthonormal basis set.
Some of what you said is nonsense though, since a 100x12 matrix has no inverse. So a can have NO inverse. At best, you can compute a'*a, and verify that is an approximate identity matrix.
norm(a'*a - eye(12))
ans =
2.2982e-15
As you can see, I did NOT check for exact equality here. Instead, compare the results, and verify the difference is small, on the order of floating point trash. NEVER compare for exact equality of floating point results.
