# How to get the Z-contour values related to scatter positions?

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Philippe Corner on 24 Nov 2020
Commented: Philippe Corner on 2 Dec 2020
The matrix M contains X, Y, Z values related to 1st, 2nd and 3rd columns respectively. It is plotted on a contour using the follwing code
X=M(:,1);
Y=M(:,2);
Z=M(:,3);
[xq,yq]=meshgrid(linspace(min(X),max(X),100),linspace(min(Y),max(Y),100));
zq=griddata(X,Y,Z,xq(:),yq(:),'cubic');
[c,h]=contourf(xq,yq,reshape(zq,100,100),'levelstep',120);
hold on
scatter(ref(:,1),ref(:,2),'filled','k') % the dots where I want to get the contour value
ref.mat contains X, Y positions that suporpose the contour from M. I would like to get the Z information associated to exactly the X,Y positions of re.mat vector only for the areas where the dots overlaps the contour as you can see in the figure:
The final result can be a matrix M2, such as 1st column (X position over the contour); 2nd column (Y position over the contour) and 3rd column the extracted Z values related to M matrix contour.

KSSV on 24 Nov 2020

#### 1 Comment

Philippe Corner on 2 Dec 2020
Hello KSSV, I solved it using the function you suggested. Thank you.
Please take a look on this loop i would like to make to eliminate some part of my data: https://www.mathworks.com/matlabcentral/answers/671943-how-create-a-matrix-that-matches-a-condition-in-comparison-with-other-matrix?s_tid=srchtitle