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how to determine each local min point?
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Hi everyone, I have a urgent question to seek for help...
I have a sine wave however, angle in the sine wave is not a constant variation of x as shown below...
x = 0: 0.00001: 4;
v = x.*exp(x/2);
t = sin(v);
plot(x,t);
My trouble is how to display each of the local xmin point?
From the plot itself i wanted to display xmin1 = 1.859, xmin2 = 2.73, and xmin3 = 3.307.
Hope to hear from anyone soon... been cracking my head for the past weeks... )':
Best Regards
Will*
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Réponse acceptée
Image Analyst
le 6 Mar 2013
Modifié(e) : Image Analyst
le 6 Mar 2013
If you have the Image Processing Toolbox, you can use imregionalmin(), like this:
% Original code
x = 0: 0.00001: 4;
v = x.*exp(x/2);
t = sin(v);
plot(x,t);
% Image Analyst's code:
minsIndexes = imregionalmin(t); % Logical array of where mins are.
% Extract the t values at those min locations;
minValues = t(minsIndexes)
% Get the x values at those mins.
minX = x(minsIndexes)
% Plot star over the mins.
hold on;
plot(minX, minValues, 'r*', 'MarkerSize', 10);
In the command window:
minValues =
0 -1.00 -1.00 -1.00 -1.00 -0.96
minX =
0 1.86 2.76 3.31 3.70 4.00
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/172132/image.png)
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