MATLAB Answers

contourc - plotting contour matrix

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John Mahoney
John Mahoney on 1 Jun 2012
Commented: Liviu Ivanescu on 2 Sep 2021 at 18:09
I would like to find the contours, manipulate them, and then plot them.
This plots contours
x = 0:0.1:1; y = 0:0.1:1;
[X,Y] = meshgrid(x,y);
Z = sin(X).*cos(Y);
[con_mat, h] = contour(x, y, Z);
To get the contour information without plotting, can use contourc.
con_mat = contourc(x, y, Z);
However, there appears to be no built-in way to plot this "contour matrix".
Any thoughts?

Accepted Answer

Darin on 5 Jun 2012
Try this: it uses cplot, which you can find on Matlab central.
If you find something more elegant, please let us all know... it MUST be buried in the Matlab library function SOMEWHERE.
function[] = plot_contourmatrix(C);
% plot_countourmatrix - Plots a contour matrix c as returned from contour
% plot_contourmatrix(C)
% Rev History:
% 06-04-12 Created
holdstate = ishold;
hold on;
i = 1;
while i<=length(C)
lev = C(1,i);
cnt = C(2,i);
i = i+cnt+1;
if ~holdstate
hold off;
test code - execute as cell
[x,y] = meshgrid(-3:.1:3);
z = sinc(hypot(x,y));
[C,h] = contour(x,y,z);
axis equal
axis equal
Johannes Korsawe
Johannes Korsawe on 26 Jan 2015
Where to find cplot? it is not longer on the FEx ?

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More Answers (1)

Liviu Ivanescu
Liviu Ivanescu on 18 Aug 2018
Edited: Liviu Ivanescu on 18 Aug 2018
Here is a way to plot contourc data containing several contours of the same value.
cnt = contourc(matrix,[-2 -2]);
szc = size(cnt);
idz = 1;
while idz<szc(2)
izi = cnt(2,idz);
cnt(2,idz) = nan;
idz = idz+izi+1;
Liviu Ivanescu
Liviu Ivanescu on 2 Sep 2021 at 18:09
you are correct

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