Finding frequency range above certain coherence threshold.

I've just created a graph that shows the coherence of two wave signals as a function of frequency. This is my script so far:

n=dataset6(:,1); u=dataset6(:,2); [P f]=cohere(n,u,8192,5,1024,512,'linear'); plot(f,P); axis([0,1,0,1]); xlabel 'Frequency (hz)' ylabel 'Coherence'

How can I now find the frequency range of the two signals above a coherence level of 0.8?