Vector Cosine

For real vectors x and y having the same length, we may compute the vector cosine by

cosxy = y' * x / ( norm(x) * norm(y) );

For complex vectors, a good measure of orthogonality is the modulus of the vector cosine:

collinearity = abs(y' * x) / ( norm(x) * norm(y) );

Thus, when collinearity is near 0, the vectors x and y are substantially orthogonal. When collinearity is close to 1, they are nearly collinear.