# How to locate the x and y co-ordinate of minimum value from a contour plot automatically ?

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I am trying to plot a contour and find it's x and y co-ordinate of the minimum value from the contour plot. Here is a sample code.
clear variables
format long
close all
clc
a = 10;
b = 20;
c_dom = 1:10;
d_dom = 11:20;
L_c_dom = length(c_dom);
L_d_dom = length(d_dom);
e = zeros(L_c_dom, L_d_dom);
for j_c = 1:L_c_dom
for j_d = 1:L_d_dom
c = c_dom(j_c);
d = d_dom(j_d);
e(j_c, j_d) = a*b*c*d;
end
end
[x, y] = meshgrid(c_dom, d_dom);
[C, h] = contour(x, y, e);
Above figure is the contour plot. Now, I need to locate the position (x and y co-ordinates) of it's minimum value automatically. Since this is a sample code so I know that the first value of variable 'c_dom' and 'd_dom' are the x and y co-odrinates. But in reality my actual code is a bit complicated and the contours are bunch of concentric circles. I checked online but I am just getting the use of min() command to get the minimum value but I didn't find any procedure to locate it's position (x and y co-ordinates). I did another technique where I found out the minimum value of the contour and plotted the value and highlighted it. After clicking at that point I can get x and y co-ordinates from the plot itself. But unfortunately it's a very tedius job and if I had to do a parametric study where my variable 'a' and 'b' are also a vector, then it is a very lengthy process. So, I need to find a way to locate x and y co-ordinates automatically. Any help will be greatly appreciated.

### 采纳的回答

Turlough Hughes 2021-8-22

Try:
[min_e,index] = min(e,[],'all','linear');
x_min = x(index);
y_min = y(index);
hold on, plot(x_min,y_min,'ok','MarkerFaceColor','k');
This gives the location of x and y (the index) corresponding to the minimum in e.
##### 2 个评论显示隐藏 1更早的评论
Turlough Hughes 2021-8-22
No problem :)

R2019b

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