Using mscohere along with the spectrogram function

Hello,

I am studying non-stationary time series using the spectrogram function in MATLAB. I am interested in analyzing the cross-spectrum of periodograms derived from the spectrogram function by taking the 2-D projection of just time and frequency coordinates at varying levels of power. But I don't know of a simple way to obtain these projections. Ideally, an answer will explain how to obtain the projections in such a way that I can then apply the mscohere function.

Any help is appreciated!