# How to find number of times graph goes back to zero

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Sharah 2014 年 6 月 15 日
コメント済み: Star Strider 2014 年 6 月 16 日
Hello everyone, I am new to MATLAB and I am currently plotting a normalised gyroscope data as in the picture below, and I am trying to count the number of the graph trying to go back to zero (on the word, number of the graph descending after reaching each peak)
For example, if I calculate it manually fromthe graph, it's around 9 times it tries to go back to zero. But I am trying to do analysis on big data so I really ned way of finding it by MATLAB.
Help me, thanks

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### 採用された回答

Star Strider 2014 年 6 月 15 日
To find the troughs, invert the ‘y’ values and use findpeaks:
Example:
x = linspace(0,250,250); % Create Data
y = 0.25*sin(0.25*pi*x) .* exp(-(x-125).^2./1000) + exp(-(x-125).^2./1000);
[pks,plocs] = findpeaks(y); % Find peaks
[trs,tlocs] = findpeaks(0.1+max(y) - y); % Find troughs
figure(1)
plot(x, y)
hold on
plot(x(plocs), y(plocs), '^r', 'MarkerFaceColor','r') % Plot peaks
plot(x(tlocs), y(tlocs), 'vg', 'MarkerFaceColor','g') % Plot troughs
hold off
grid
produces:
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Star Strider 2014 年 6 月 16 日
My pleasure!
I saw your other post and suggested a solution.

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