How we can define the same number of contour vertices (points)in each level?
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atefe moheyseni
on 27 Jun 2023
Answered: Mathieu NOE
on 27 Jun 2023
Hi there,
I used the contour function for my issue and extracted the points that made each level but the number of points(vertices) in each level is different. I need the same points in each levels, How I can define the same number of contour vertices (points)in each level?
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Mathieu NOE
on 27 Jun 2023
you could resample the data with the same number of points for all levels using interp1
Accepted Answer
Mathieu NOE
on 27 Jun 2023
hello again
this is the code I was suggesting above
now all the level lines have same number of samples N = 50 here.
if you need to have a more uniform distribution there is a bit of extra work involving transforming from cartesian to polar coordinates and resample the data in the polar coordinates system instead.
x = 0:0.1:2;
y = 0:0.1:3;
[X,Y] = meshgrid(x,y);
Z = X.*exp(-X.^2-(Y-1.5).^2);
[cm, h] = contourf(X,Y,Z);
[contourTable, contourArray] = getContourLineCoordinates(cm);
% Fex : https://fr.mathworks.com/matlabcentral/fileexchange/74010-getcontourlinecoordinates
% Show all lines that match the kth level
hold on
for k = 5:7
levelIdx = contourTable.Level == h.LevelList(k);
x = contourTable.X(levelIdx);
y = contourTable.Y(levelIdx);
% resample the data to have always the same nb of points
N = 50;
nx = numel(x);
xi = interp1((0:nx-1)/(nx-1),x,(0:N-1)/(N-1));
ny = numel(y);
yi = interp1((0:ny-1)/(ny-1),y,(0:N-1)/(N-1));
plot(xi, yi, 'r*-', 'MarkerSize', 10)
end
hold off
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