Find the local and global maxima and minima

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Priyadarshini Nair
Priyadarshini Nair 2021-10-27
回答： Drishan Poovaya 2021-11-1
Find the local and global maxima and minima for the function f(x)=sin|x|, in an interval I = (−2π, 2π)
  1 个评论
Jaya
Jaya 2021-10-27
You might consider reading this page. It has got examples. You will be able to do for your function then. https://www.mathworks.com/help/symbolic/maxima-minima-and-inflection-points.html
As anyway you have tagged this question under the tag homework with no sample code, I have tried providing a resource for you to read rather than soving it by myself!

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回答（1 个）

Drishan Poovaya
Drishan Poovaya 2021-11-1
One option is to use ‘findpeaks’ in the Signal Processing Toolbox. It will give you the maximum (and indirectly the minimum) values and their index locations. If ‘y’ is the vector that produced the plot, to find the maxima and minima:
n = -2*pi:0.01:2*pi;
y = sin(abs(n));
plot(n,y);
[Maxima,MaxIdx] = findpeaks(y);
%plot maxima
hold on;
plot(n(MaxIdx),Maxima,'r*');
[Minima,MinIdx] = findpeaks(-y);
%plot minima
plot(n(MinIdx),-Minima,'g*');
hold off;
This will plot the maxima in red and the minima in green. You can refer to the Maxima and Minima arrays to get the maximum and minimum values respectively
Refer to the documentation for findpeaks below:
https://www.mathworks.com/help/signal/ref/findpeaks.html

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