How does the matlab contourf function work?

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Jenna
Jenna 2020-3-17
回答： darova 2020-3-17
How does the matlab contourf function work? The function describes, "MATLAB® automatically selects the contour lines to display." -- but how does Matlab automatically select the lines? (Histogram? some other statistic?)
  2 个评论
Ameer Hamza
Ameer Hamza 2020-3-17
The documentation does not specify how MATLAB calculates the contour lines internally. Also, you cannot see the internal implementation of the function, which draws the contour. However, you can specify the levels input of the contour function to set the value of contour lines manually.
Jenna
Jenna 2020-3-17
Yes. I know. I'm wondering if someone who works at matlab can describe the functionality a bit for me. Thanks

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回答（1 个）

darova
darova 2020-3-17
I pretty sure that MATLAB checks each 'plane' (that close to some level) on intersection
Simply reducing the task to plane-plane intersection
clc,clear
cla
[X,Y] = meshgrid(-2:0.1:2);
Z = X.^2+Y.^2-3;
p = surf2patch(X,Y,Z);
surf(X,Y,Z,'edgeColor','none')
alpha(0.5)
f = p.faces;
v = p.vertices;
axis vis3d
for i = 1:size(f,1)
ix = f(i,:);
sgn = sign(v(ix,3));
if abs(sum(sgn)) < 4 % if 'z' values have different sign
patch('faces',ix,...
'vertices',v,...
'faceColor','none')
pause(0.1)
end
end

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