how to find max and min value within a certain range of a plot

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ZENONG 2023-4-12

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评论： Star Strider 2023-4-13

Hi, I'm using plot function to identify second wave and measure it's frequency, so is there any way for me to get timeseries of the max and min value within the second wave range directly without have to search them in csv files. Thank you.

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Antoni Garcia-Herreros 2023-4-12

Do you havethe mat file?

ZENONG 2023-4-13

tek0000ALL.fig

This is the plot file and want to know how to find the timeseries of first upper peak and second lower peak.

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Answer 1

Star Strider 2023-4-12

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Use the bounds function on the specific plot argument.

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Star Strider 2023-4-13

在 MATLAB Online 中打开

tek0000ALL.fig

EDIT — (13 Apr 2023 at 17:34)

I am not certain what you want. This provides the peak values, locations, and frequencies of each peak, valley, and complete wave. (The frequencies are not printed on the plot because there is not room enough for them.)

I = openfig('tek0000ALL.fig');

grid

Lines = findobj(I, 'Type','line');

xv = Lines.XData;

yv = Lines.YData;

Tss = [mean(diff(xv)) std(diff(xv)) median(yv)];

Fs = 1/Tss(1);

[pks,plocs] = findpeaks(yv, 'MinPeakProminence',max(yv)/4);

[vys,vlocs] = findpeaks(-yv, 'MinPeakProminence',max(-yv)/4);

zxix = find(diff(sign(yv-median(yv))));

rtbl = find(zxix>max(vlocs),1,'first');

zxix = zxix(1:rtbl);

periodv = diff(xv(zxix));

pervbfr = buffer(periodv,2);

freqv = 1./sum(pervbfr) % Frequency Of Each Complete Wave

freqv = 1×4

1.0e+06 * 0.8039 2.8090 1.2136 0.5869

figure

plot(xv, yv)

hold on

hold off

grid

yline(median(yv))

text(xv(plocs), pks, compose(['(%.2fx10^{-5}, %.3f)'],[xv(plocs)*1E5; pks].') )

text(xv(vlocs), -vys, compose(['(%.2fx10^{-5}, %.3f)'],[xv(vlocs)*1E5; -vys].') )

.

ZENONG 2023-4-13

Thank you!

Star Strider 2023-4-13

As always, my pleasure!

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