How to get data gradient and how to locate significant changes of the gradient? I'm trying to locate the first "turning point" of the plot below. Other turning points can be ignored.
MATLAB: Find turning point in data
gradientplottriangle threshold
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Hi,
basically there are two ways described there:
1- triangle thresholding
2- local maxima of curvature
i prefer the first one as i think it directly answer your question (the second one is for more spesific tasks)
% here is a small code to help you start
% Lets say your data are defined in (x,y) values
% then do the following
time = x;% here you should enter your data name
data = y;% here you should enter your data name% Basically it draws a line from the peak to the tail and then draws
% perpendicular lines from that hypotenuse line to the curve.
% The longest (smollest) perpendicular line from the hypotenuse to the curve
% indicates the "corner" of the curve. Maybe that will work for you. (this discribtion was taken from the reference before)
% Two endpoints on the curve "data"
x = [time(1) time(end)];y = [data(1) data(end)];% The slope of the line connecting the two endpoints
m = ( y(2) - y(1) )/( x(2) - x(1) );pm= - 1 / m;figure();hold allhP = plot(time,data,'b',x,y,'g',x(1),y(1), 'ro');grid onyl = ( (m * time) + (m^2 * data) - (m * x(1)) + y(1) )/(1+m^2);xl = T1 - m*(yl - data);d2 = (xl - time).^2 + (yl - data).^2;perpDist = d2;[val_max, idx_max] = max(perpDist);[val_min, idx_min] = min(perpDist(2:end-1));[val_maxL, idx_maxL] = max(perpDist(1:idx_min));plot(time,data,'b',time(idx_max),data(idx_max),'ro',time(idx_min),data(idx_min),'ro',time(idx_maxL),data(idx_maxL),'ro');grid on;hold all; plot(time,perpDist); hold offI hope this answer your question (how accurate the point will depend on your massy data)
How about using the ISMEMBER function?
Cellarray_2(ismember(Cellarray_3,Cellarray_1))ans = 1 10 34 4 1 1
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