summing the ith frequencies with the ith amplitudes^2 from a spectrogram of a Harmonic

From http://i.imgur.com/Arctu.png where fi is the ith frequency component, ui is the amplitude of said frequency component, K is a constant, tau is time and t is the time integration variable I have used the following to spectrogram a harmonic that will be processed by the attached eqn:

[S, F, T, P] = spectrogram(A(800000:6*800000), 2^15, 1, (1:0.1:20)*10^4, 1/1.2e-7)

I don't have any problems with the first half of the eqn in the link, but the second half confuses me. You can't square a vector and I'm not certain that amplitude is P, or if frequency is taken from S or F. Would you take the peaks in the amplitude vector or take it time segment by time segment?

I appreciate any help.

Answer 1

[Matt Fig]

It is not the vector that is being squared, but each component.

A = [1 2 3 4];
A.^2  % Notice the '.' - it matters!

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EDIT In response to your 'answer' below.

I don't know which variables form spectrogram you should be using. It is up to you to understand the problem and your particular application. For example, I don't know where you got those equations you posted, only you know that. Perhaps reading the SPECTROGRAM doc will help.

[Oleg Komarov]

You were too fast :)

Answer 2

[Gareth]

Ok, but which variables from spectrogram should I be using?