Best method to find maximum and minimum second derivatives of function
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Hello,
I created this script to find the maximum and minimum second derivatives of a given array. I was wondering what possible improvements there could be. A sample image is attached for reference.
f = tracks_2(:,2);
windowWidth = 37;
polynomialOrder = 3;
f = sgolayfilt(f, polynomialOrder, windowWidth);
plot(f);
f1 = diff(f); %diff intstantly returns the derivative
plot(f1)
f1 = sgolayfilt(f1, polynomialOrder, 37);
f2 = diff(f1); %second derivative
plot(f2)
f2 = sgolayfilt(abs(f2), polynomialOrder, 15);
[pks,locs] = findpeaks(f2,'MinPeakProminence',0.05); %maximum peaks
plot(1:length(f),f,locs,f(locs),'*')
2 Comments
John D'Errico
on 17 May 2020
Edited: John D'Errico
on 17 May 2020
IF you are going to smooth your data using a Savitsky-Golay filter, then you should arguably use a similar filter to give you the estimated first and second derivatives directly.
Note that I posted a function called movingslope on the file exchange. It does exactly that, at least for the first derivative.
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