Modal Phase Collinearity (MPC) is a parameter used to quantify the complexity of a mode. It is calculated using the following equation:

where

= the real part of the mode shape

= the imaginary part of the mode shape

This parameter is bounded between 0 and 1, giving a lower value for a more complex mode shape. A complex-valued mode is only considered if it cannot be converted to a real-valued vector by multiplication with a scalar. That excludes proportionality between the real and imaginary parts of a mode shape.

The MPC value is shown in the MAC Frequency Worksheet for complex modes.