using find-command to find max or min value

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Please I need your help to estimate the value of min or max of abs(Y) and its corresponding (X) for attached curve (X versus X ) using (find)-command. In addition want plot a line of corresponding (X) and (Y).
Thanks in advance for all.
Best Regards;
  1 Comment
Moustafa Abedel Fattah
Moustafa Abedel Fattah on 26 Jun 2022
Thanks a lot for your quick response as usual. It is works very good and I will more appreciate if you solve it also with (find) command.
Thanks in advance
Best Regards;

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Accepted Answer

Star Strider
Star Strider on 26 Jun 2022
This is relatively straightforward. Use max with two outputs:
x = 0:13;
y = randi(25,1,14)/100;
[ymax,idx] = max(y)
ymax = 0.2400
idx = 13
figure
plot(x, y)
hold on
plot([1 1]*x(idx), [min(ylim) ymax], '-r')
plot([0 x(idx)], [1 1]*ymax, '-r')
hold off
grid
Experiment with your data.
.
  1 Comment
Star Strider
Star Strider on 27 Jun 2022
As always, my pleasure!
Using find is straghtforward —
x = 0:13;
y = randi(25,1,14)/100;
idx = find(y == max(y))
idx = 10
figure
plot(x, y)
hold on
plot([1 1]*x(idx), [min(ylim) y(idx)], '-r')
plot([0 x(idx)], [1 1]*y(idx), '-r')
hold off
grid
That requires essentially the same code.
.

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More Answers (1)

Image Analyst
Image Analyst on 26 Jun 2022
I prefer using the find function in combination to find max and min locations. The reason being if the max occurs at more than one location, max only gives you the location of the first one. I've asked them for many, many years to return the index(es) of all max in the vactor.
y = [1 3 2 3 0] % Max at index 2 and 4
y = 1×5
1 3 2 3 0
[maxValue, indexes] = max(y) % Only gives you the one at index 2 not at 4.
maxValue = 3
indexes = 2

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