how to get the maximum amplitude value from the Python PSD function

Question

I plotted this spectrum with the following code:

[Y,F]=psd(samples, NFFT=1024, Fs=sdr.sample_rate/1e6, 
Fc=sdr.center_freq/1e6, noverlap=0)
xlabel('Frequency (MHz)')
ylabel('Relative power (dB)')           
max=np.max(Y)
print(max)

but then I get

max=0.000458510518667

Actually, if I print the values of Y, I get:

[ 8.60400008e-06 7.85361760e-06 9.00300444e-06 ...,
9.55738417e-06 1.14888955e-05 1.12340323e-05]

maybe I need to do something else to get the amplitudes that I see in the plot?

10*log(0.000458) is roughly -33 dB, so I don't see what's wrong with the result you get. Maybe you first tell us in how far what you get is not what you expect? — ImportanceOfBeingErnest, Nov 14 '17 at 16:21
oh, I thought the result would be on dB!! I wasn't expecting that, sorry for the confusion. Should I delete this question? thank you! — Contact-us Behind The Sciences, Nov 15 '17 at 09:47
It depends. If you think that it could be useful for future readers, you may leave it here and provide an answer to it yourself. If you don't think so or if you don't want to answer it, you may delete it. — ImportanceOfBeingErnest, Nov 15 '17 at 09:49
I think it may be useful for someone else who is learning Python :) However, I think you could get some "points" if you answer the question :D if you don't want to do it, I'll do it but I think it'd be fair if you do it — Contact-us Behind The Sciences, Nov 15 '17 at 10:14
It would be fair yes, but I have enough points, and I don't need to earn reputation by converting a ratio to dB. — ImportanceOfBeingErnest, Nov 15 '17 at 10:16

score 1 · Accepted Answer · answered Nov 15 '17 at 10:32

The result isn't given in dB so actually:

10*log(0.000458) = -33 dB (approx.)

Therefore, the previous code is correct and you can use it if you need to get the maximum value of the PSD function. You could add this code:

    max=np.max(Y)
    log=10*math.log10(max)
    print(max)
    print(log)

I realize about this thanks to the user @ImportanceOfBeingErnest who is an expert in the Python library I'm using, matplotlib.

how to get the maximum amplitude value from the Python PSD function

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