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Rendering issues in Matlab R2014b version when using patch

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Giorgos Papakonstantinou
Giorgos Papakonstantinou on 5 Dec 2014
I am using patch to shade an area in a graph. The code that I am using is simple:
lm = 0;
s = 1:1000;
d = [ones(1, 100) zeros(1, 800) -1*ones(1, 100)];
xdata = [s(1) s s(end)];
ydata = [lm d lm];
patch(xdata, ydata, ones(size(xdata)));
In the attachment, the left figure is produced from R2014b version and the right from version R2012b.
Is there a workaround to deal with this problem? Have you also noticed it?
Thank you very much in advance.

Answers (3)

Titus Edelhofer
Titus Edelhofer on 5 Dec 2014
Hi,
I think you need to add the line at the zero:
lm = 0;
s = 1:1000;
d = [ones(1, 100) zeros(1, 800) -1*ones(1, 100)];
xdata = [s(100) s(1) s s(end) s(end-99)];
ydata = [lm lm d lm lm];
patch(xdata, ydata, ones(size(xdata)));
I'm not sure why it works fine in 12b ...
Titus
  4 Comments
Mike Garrity
Mike Garrity on 5 Dec 2014
It sounds like another instance of this bug, but you should send it to support to make sure they're tracking it.
I think that one had to do with multiple edges which were colinear, but didn't have coincident vertices.

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Giorgos Papakonstantinou
Giorgos Papakonstantinou on 5 Dec 2014
Thank you Mike for you input. The simplest workaround that can overcome this problem is setting the value lm very low. i.e.
lm = 1e-5; % practically zero
s = 1:1000;
d = [ones(1, 100) zeros(1, 800) -1*ones(1, 100)];
xdata = [s(1) s s(end)];
ydata = [lm d lm];
patch(xdata, ydata, ones(size(xdata)));
This can fix it for the moment, as you can see below:

matt dash
matt dash on 5 Dec 2014
I suppose this qualifies as a bug, but it seems like a bad coding practice. If you know you want the patch to produce a series of bars, like a histogram, a better option is (at least to me) to plot each bar as a face of the patch by supplying all 4 vertices. I don't think the overhead of making each bar a separate face of the patch will be noticeable, even for very complex plots.
  1 Comment
Giorgos Papakonstantinou
Giorgos Papakonstantinou on 6 Dec 2014
Yes I agree with you. However here, I am not using patch to produce some bars. I use it to patch an area. I just gave a simple example which appears like patched bars, to illustrate the problem.

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