My current problem is that I have a huge set of data for a pressure rise caused by a train entering the tunnel. I would like to find the values of x whenever the pressure rises crosses a pressure threshold and would like to be able to work out the difference between the pair of x's (should only be one pair)
MATLAB: Finding x for when y equals a certain value
xy
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‘find peaks between heights y1 and y2’
That option doesn’t exist, but you can do something similar with two separate findpeaks calls and a setdiff call. I don’t have your data, but the code would be something like this:
x = linspace(0, 5*pi, 250);y = 0.25*sin(x).*(0.1*cos(5*x));[pks1,locs1] = findpeaks(y, x, 'MinPeakHeight',0.01);[pks2,locs2] = findpeaks(y, x, 'MinPeakHeight',0.02);[C, ia] = setdiff(locs1, locs2, 'stable');MidPks = [pks1(ia); locs1(ia)];figure(1)plot(x, y)hold onplot(MidPks(2,:), MidPks(1,:), '^r') hold offgrid
I would do something like this:
x = [1:17]*10; % Create Data
y = [0 1 0 2 0 9 0 3 0 1 0 2 0 9 0 3 0]*0.25; % Create Data[pks1,locs1] = findpeaks(y, x, 'MinPeakHeight',2);[pks2,locs2] = findpeaks(-y, x);pk1_start = locs2(find(locs2 < locs1(1), 1, 'last')); % Start Of First Peak
pk1_end = locs2(find(locs2 > locs1(1), 1, 'first')); % End Of First Peak
... then do the same for the second peak, ‘locs1(2)’. With the start- and end-points, you can define the entire peak.
This makes some assumptions about your data, since I do not have them to work with. You will probably have to experiment with this idea for it to work with your data.
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