How to get contour plot and line plot intersection values/ coordinates
12 次查看(过去 30 天)
显示 更早的评论
I am plotting a 3D graph and a contour of the same. Then I plot few lines on the contour plot. I want to know the value of the contour where the line crosses the contour and also the coordinates where intersection happens. Can anyone please help me with this
0 个评论
回答(1 个)
Kelly Kearney
2013-7-16
I assume by 3D graph with contour, you mean you have 3D data represented in 2D by a contour plot? Or do you mean something like contour3 or isosurface?
Assuming the former, the coordinates of the contour lines generated via
[c,h] = contour(x,y,z);
are found in the c matrix. There are a few File Exchange functions (like contourcs) that can simplify the task of extracting those coordinates.
If you have the Mapping Toolbox, polyxpoly can calculate the line intersections. Otherwise, there are a bunch of FEX entries to calculate the intersections of two lines/curves (like this one).
3 个评论
Kelly Kearney
2013-7-19
Yes, to use the contourcs function, you need to download it from the File Exchange, and then either place it in the same folder as where you are working, or add it to your path (You can read up on that under the "Search Path" section of the documentation).
Here's a quick example of how to use those functions to calculate intersections:
% Some example data
[x,y,z] = peaks;
% Calculate the coordinates of the contour lines
% (here, just the contour line at z = 0)
C = contourcs(x(1,:),y(:,1),z,[0 0]);
% Coordinates of the intersecting line
xln = [0 0];
yln = [-3 3];
% Use polyxpoly to find intersections
for ic = 1:length(C)
[xint{ic}, yint{ic}] = polyxpoly(xln, yln, C(ic).X, C(ic).Y);
end
xint = cat(1, xint{:});
yint = cat(1, yint{:});
% Plot the results
figure;
contour(x,y,z,[0 0], 'k');
hold on;
plot(xln, yln, 'b');
plot(xint, yint, 'r*');
另请参阅
类别
在 Help Center 和 File Exchange 中查找有关 Contour Plots 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!