# Need half of my contour plot

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Maryam on 18 Jul 2013
Hello I have a contour of the pressures over a surface. Basically, I had vectors x and y which were locations on the surface and on each location, I had a value for pressure. I have a rectangular plot. I was wondering if there is a way to split my plot from the diagonal and show just the results for either upper or lower triangles?
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### Accepted Answer

Kye Taylor on 18 Jul 2013
Edited: Kye Taylor on 18 Jul 2013
Check out the tril and triu functions. For example if you have data similar to
[x,y]= meshgrid(-1:.05:1);
z = x.^2+y.^2;
contour(x,y,z)
Try something like
zLowerTri = tril(z);
contour(x,y,zLowerTri)
Since contour plots with the origin at lower left instead of upper right, you may prefer either
zLowerTri = tril(z);
contour(x,y,zLowerTri)
axis ij
or
contour(x,y,fliplr(tril(fliplr(z))))
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Pourya Alinezhad on 19 Jul 2013
use "nan" as i mentioned below to make that part invisible... functions you use {ex:tril(z)} replace the data values with zero,which itself could be a data!!!
Maryam on 19 Jul 2013
Thank you very much. I now have what I wanted.

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### More Answers (1)

Pourya Alinezhad on 18 Jul 2013
Edited: Pourya Alinezhad on 18 Jul 2013
hello maryam, run following lines of code.
x=0:0.1:10;
y=x;
j=1;
z=meshgrid(x,y);
h=ones(length(x),length(x))*nan;
for i=1:length(x)
for j=1:length(y)
if i>j
h(i,j)=z(i,j);
end
end
end
surf(sin(h)./sqrt(h))
figure
contourf(sin(h)./sqrt(h))
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