Find the X,Y coordinates for a specific value

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Ilias Iord 2017-4-9

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https://ww2.mathworks.cn/matlabcentral/answers/334509-find-the-x-y-coordinates-for-a-specific-value

评论： Star Strider 2017-4-9

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Hello to all, since it's my first time here!

I have two vectors of co-ordinates (1-n) for X and Y and a surface (S) with n-n corresponding values.

The question is, how can I get the X, Y values for the single minimum value of S.

%calculation of drawdown in confined aquifer
clear
clc
% Parameter and variable values
xabs=3000;
yabs=xabs;
xmin=-xabs;
ymin=-yabs;
x=xmin:50:xabs;
y=ymin:50:yabs;
x1=1500;
y1=600;
x2=700;
y2=1800;
x3=1200;
y3=900;
x4=500;
y4=800;
rw=0.3; %well radius
rinf1=2000; %m   radius of influence
rinf2=3000;
rinf3=5000;
rinf4=500;
k=2.58; %m/day
q1=1200; %m3/day
q2=1500;
q3=2000;
q4=500;
a=45; % m (confined aquifer width)
hw=30; %m ( well drawdown depth)
s1=drawdown(xabs,x1,y1,rinf1,k,q1,a);
s2=drawdown(xabs,x2,y2,rinf2,k,q2,a);
s3=drawdown(xabs,x3,y3,rinf3,k,q3,a);
s4=drawdown(xabs,x4,y4,rinf4,k,q4,a);
s=s1+s2+s3+s4;

"Drawdown" is the function that calculates S for the well data. I need the coordinates for the minimum peak.

Thanks a lot guys!

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Answer 1

Star Strider 2017-4-9

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https://ww2.mathworks.cn/matlabcentral/answers/334509-find-the-x-y-coordinates-for-a-specific-value#answer_262399

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Since ‘S’ appears to be a matrix and not a function, try this:

[r,c] = min(S);

This returns the row and column indices of the first minimum the function encounters. Since I am not certain what ‘x’ and ‘y’ represent, I will let you assign them with respect to ‘r’ and ‘c’.

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Ilias Iord 2017-4-9

编辑：Ilias Iord 2017-4-9

Thank you Star Strider!

I do not need the indices of the Minimum's location in the "S" matrix, I need the X,Y coordinates (from the meshgrid) on which this minimum is encountered. For example, in the image I uploaded, I need X=1200 & Y=900 (