# How to make contour plot of two matrices in MATLAB?

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Araz Garaz on 27 Nov 2022
Commented: Star Strider on 27 Nov 2022
I have two data files (Data_file1 and Data_file2) to do a comparison on.
Data files both are matrices with 1 row and 55 columns, which represent 55 points. The points are very similar in value, So plotting them as points wouldn't give a good figure for demonstrating differences. This is why I want to plot each point as a contour.
Here is the code I generated, it technically should work, but somehow it doesn't. Can anyone spot any error that I can't see?
figure;
sm=smithplot(gca);
hold on
NumPowCon=3;
x = linspace(-1,1,55)';
y = linspace(-1,1,55)';
[X,Y] = meshgrid(linspace(min(x),max(x)),linspace(min(y),max(y)));
F = TriScatteredInterp(x,y,Data_file1);
Z = F(X,Y);
contour(X,Y,Z,NumPowCon,'r-')
F = TriScatteredInterp(x,y,Data_file2);
Z = F(X,Y);
contour(X,Y,Z,NumPowCon,'b--')
##### 2 CommentsShowHide 1 older comment
Araz Garaz on 27 Nov 2022
Thanks for the comment. But it stops at the first contour ploting. The error is 'Xdata' and YData' must be equal the number of columns and rows in 'ZData'. I will add the data files to test the code if you can.

Star Strider on 27 Nov 2022
Data files both are matrices with 1 row and 55 columns, which represent 55 points.
They are vectors by definition, and it is not possible to plot a contour of a vector.
You could vertically concatenate the two row vectors to create a (2x55) matrix and then take the contour of that. I am not certain how meaningful that would be.
It would be necessary to have the vectors to work with in order to determine if it would be possible to do anything with them. For example, if they are ‘z’ vectors, do they have corresponding ‘x’ and ‘y’ vectors that could indicate that they are actually gridded and so could be reshaped to each create a surface?
.
Star Strider on 27 Nov 2022
As always, my pleasure!

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