Methods for smoothing contour lines
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Andrew Sol
el 20 de Oct. de 2022
Comentada: Star Strider
el 21 de Oct. de 2022
I have a database P with columns X, Y and Z (file above):
N = 150; % Number Of Points Desired
xv = linspace(min(P(:,1)), max(P(:,1)), N);
yv = linspace(min(P(:,2)), max(P(:,2)), N);
[X,Y] = ndgrid(xv, yv);
Z = griddata(P(:,1), P(:,2), P(:,3), X, Y);
contourf(X, Y, Z, 35)
Zi = interp2(P(:,1), P(:,2), P(:,3), X, Y) ;
With the code above, I get the following plot:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1163243/image.png)
How to make contour lines neater and smoother?
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Star Strider
el 20 de Oct. de 2022
Editada: Star Strider
el 20 de Oct. de 2022
I dislike going to external sites.
Increasing ‘N’ would be the option I would use, initially experimenting with 250 and perhaps 500 or greater, depending on the available memory and the result provided. That should increase the resolution of the vectors, and therefore the resolution of the matrices derived from them.
EDIT — (20 Oct 2022 at 15:45)
Using the supplied data —
LD = load(websave('P','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1163343/P.mat'));
P = LD.P;
N = 500; % Number Of Points Desired
xv = linspace(min(P(:,1)), max(P(:,1)), N);
yv = linspace(min(P(:,2)), max(P(:,2)), N);
[X,Y] = ndgrid(xv, yv);
Z = griddata(P(:,1), P(:,2), P(:,3), X, Y);
figure
contourf(X, Y, Z, 35)
I looked at the first column of ‘P’ to see if reshaping would work. It will not, because the first indices of the different unique values of ‘P(:,1)’ do not have constant distances between them.
The data simply do not appear to be smooth (i.e. may have limited precision), and that is reflected in the contours even with a relatively high precision in the interpolating matrices.
This is likely as good as it gets.
.
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