# contourc - plotting contour matrix

33 ビュー (過去 30 日間)
John Mahoney 2012 年 6 月 1 日
コメント済み: Liviu Ivanescu 2021 年 9 月 2 日
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?
John

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### 採用された回答

Darin 2012 年 6 月 5 日
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
figure(gcf);
holdstate = ishold;
hold on;
i = 1;
while i<=length(C)
lev = C(1,i);
cnt = C(2,i);
cplot(C(1,i+(1:cnt)),C(2,i+(1:cnt)),repmat(lev,1,cnt));
i = i+cnt+1;
end;
if ~holdstate
hold off;
end;
return
test code - execute as cell
figure(1);
[x,y] = meshgrid(-3:.1:3);
z = sinc(hypot(x,y));
[C,h] = contour(x,y,z);
axis equal
figure(2)
plot_contourmatrix(C);
axis equal
##### 2 件のコメントなしを表示なしを非表示
John Mahoney 2014 年 12 月 4 日
Thanks Darin. I was using something similar, but was checking for integer values in C(2,:). This fails (almost never) when the y value is an integer. Yours does not have this problem.
It would be ideal to have a Matlab function not only for plotting this matrix, but for extracting the points in these contours (would use the same code as above.) as folks often want to process these contours before plotting etc.
Johannes Korsawe 2015 年 1 月 26 日
Where to find cplot? it is not longer on the FEx ?

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### その他の回答 (1 件)

Liviu Ivanescu 2018 年 8 月 18 日

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;
end
plot(cnt(1,:),cnt(2,:))
##### 3 件のコメント1 件の古いコメントを表示1 件の古いコメントを非表示
Eduardo Vicente Wolf Trentini 2021 年 9 月 2 日
in the first line did you mean "cntr = contourc(matrix,[-2 -2]);"?
i think you forget the "r" in cntr
thanks
Liviu Ivanescu 2021 年 9 月 2 日
you are correct

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