How to ignore specific parts of a plot ??
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Ceren GURKAN
on 17 Jun 2014
Commented: Jason Nicholson
on 18 Jun 2014
Hello everybody,
I have the attached plot, the circles and the ellipse are holes so in my plot I want to leave blank inside the circles and the ellipse I do not want the lines cut through those.
Any suggestions how to do that??
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/164438/image.jpeg)
2 Comments
dpb
on 17 Jun 2014
How were they created? Is there data inside the boundaries; if so turn it to NaN and see if that's enough of a clue to the handle graphics to not display those locations.
Accepted Answer
Jason Nicholson
on 17 Jun 2014
Given the mesh I see in your picture, the following works becuase your elements are not distorted and your edges are very close to linear:
xg = linspace(min(X(:,1)), max(X(:,1)), 100);
yg = linspace(min(X(:,2)), max(X(:,2)), 100);
[xg, yg] = ndgrid(xg, yg);
elementNumber = tsearchn(X, T(:,1:3), [xg, yg]);
nans = isnan(elementNumber);
Fx = TriScatteredInterp(X_plot(:,1), X_plot(:,2), qx);
Fy = TriScatteredInterp(X_plot(:,1), X_plot(:,2), qy);
qxg = Fx(xg, yg);
qyg = Fy(xg, yg);
qxg(nans) = NaN;
qyg(nans) = NaN;
figure(1); hold on;
hl = streamslice(xg, yg, qxg, qyg);
set(hl, 'color', 'b','Linewidth',0.5);
4 Comments
Jason Nicholson
on 18 Jun 2014
I can look at more tonight. Can you post the qx and qy vectors so that I can look closer at the problem?
More Answers (1)
Jason Nicholson
on 17 Jun 2014
Edited: Jason Nicholson
on 17 Jun 2014
Can you post the data that made this plot?
My hunch is the main issue is TriScatteredInterp used Delaunay triangulation of your data and the holes were meshed in the TriScatteredInterp function. If instead you used the original triangulation to do the interpolation, then you should be able to get the desired result. If you can post the mesh, I can post code that does the interpolation without TriScatteredInterp. My code would rely on tsearchn to locate the element that contains point [xg, yg] and then use the local barycentric coordinates to interpolate. The key though is to use your mesh to define connectivity of your points. Points [xg, yg] that are not contained in an element will be returned as nan's and thus will not show up on the plot. So something like this:
[elementNumber, localElementCordinates] = tsearchn(xyCordinates, myTriangulation, [xg, yg]);
notNan = ~isnan(elementNumber);
qxg = nan(size(xg,1), 1);
qyg = nan(size(yg,1), 1);
% connectivity of elements containing points
elementsContainingPoints = myTriangulation(notNan,:);
% weights of nodes for given uq points that are contained in elements
weights = localElementCordinates(notNan,:)
qxg(notNan) = sum(weights.*qx(elementsContainingPoints),2);
qyg(notNan) = sum(weights.*qy(elementsContainingPoints),2);
3 Comments
Jason Nicholson
on 17 Jun 2014
Edited: Jason Nicholson
on 17 Jun 2014
Okay so may answer may not work because your mesh has 6 node parabolic triangles rather than 3 node linear triangles.
Really you need a set of tools for parabolic triangles: locate an element containing a given point barycentric coordinates (local weighted coordinates of the nodes).
Do understand what TriScatteredInterp is doing when you use natural neighbor interpolation?
I'll have to think about this a little more.
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