cpsd output vector differs from plotted result

Question

DLR 2024-8-1

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2141911-cpsd-output-vector-differs-from-plotted-result

评论： Voss 2024-9-5，0:38

When using cpsd to calculate the cross power spectral density, I've noticed that the plot produced by directly running the command with no output arguments is slightly different from what I get when I run it with an output argument and plot that output myself.

The following code (attached along with example signal file) produces the figure below.

signalx = randn(2e4,1);
signaly = randn(2e4,1);
window = length(signalx)/3;
noverlap = round(0.9*window);
fs = 2074;
[Pxy,F] = cpsd(signalx,signaly,window,noverlap,[],fs);
plot(F./1000,10.*log10(real(Pxy)))
hold on
cpsd(signalx,signaly,window,noverlap,[],fs);
legend('CPSD output','CPSD direct plot')

I'm trying to run cpsd column-wise on a pair of very large matrices. Obviously I can't just plot them one by one, but I don't know how to interpret this difference and I'm not sure if I trust the output argument. Does anyone know what's going on here? Thanks!