how to graph function

[y,Fs] = audioread('C:\Users\Casper\Desktop\3.3V.wav');

L=length(y); % series length

;

f = Fs/2*linspace(0,1,L/2+1); % single-sided positive frequency

X = fft(y)/L; % normalized fft

PSD=2*abs(X(1:L/2+1)); % one-sided amplitude spectrum

figure,plot(f,PSD);

grid

xlabel('freq(Hz)')

ylabel('amplitude')

Answer 1

[Star Strider]

Try this —

idx = (f <= 1500) & (f <= 1800)
[rpm, freq] = findpeaks(PSD(idx), f(idx), 'MinPeakHeight',0.75E-3)

Without the data, I cannot experiment with that, however it should return the peak value as ‘rpm’ and the frequency as ‘freq’. If it does not, experiment with 'MinPeakProminence' instead of 'MinPeakHeight' since it cannot be determined from the plot that there are not more components to the desired peak.

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[burak Kalayoglu]

Thank you king

[Star Strider]

As always, my pleasure!

.

Answer 2

[Voss]

You could use Data Cursor to create a datatip, or you could try something like this:

idx = find(f(:) > 1000 & f(:) < 2500 & PSD(:) > 0.00075);

[burak Kalayoglu]

I want to find a value1698 (signed point in graph) but ı cant , ı want to find signed point and after ı can find rpm this signal

[Voss]

What does this do?

f(1698)
PSD(1698)

[burak Kalayoglu]

Because I want to see what corresponds to the same psd value in different signals