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San
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MATLAB 2014b: patch() function not coloring the right region

Asked by San
on 28 Oct 2014
Latest activity Commented on by Image Analyst
on 8 Nov 2014
I was using patch() function to plot some data and it doesn't appear to place to color in the correct region. If you view the figure below (in the bottom panel). You will see that the boundary where I set for the color filled in or totally ignored. The error occurs at 7PM, 11PM, 5AM, 7AM etc. The red stars indicates the points for the patch and the red dotted line indicates the boundary where the patch tool suppose to place the color.
However if you zoom in for a patch (2nd figure), the color placement became corrected. I did not do anything to the patch except using the ZOOM tool in on the figure to zoom in.
If someone has a solution and would like to share. I would appreciate your help. Thank you.
-San-

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3 Answers

Answer by dami
on 5 Nov 2014

I have the same problem with 2014b version. I don't understand how the zoom should solve the problem: also in your second figure not all the lines are patched properly.
I tried to replicate the problem as I described here.
It seems to be a bug of the new release, affecting patch and fill functions with concave polygons.

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I totally agree with your thoughts. I am not sure when will Mathworks will release an update to fix this problem.

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Answer by Image Analyst
on 6 Nov 2014

Maybe try fill() or area() instead of patch()?

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I suggest that whenever you have polygons where the edge intersects or crosses another edge, you plot it as two or more separate regions.

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Answer by dami
on 6 Nov 2014

Both fill() and patch() functions give wrong results and area() function is different because does not support concave polygons.
Is there a way to report to MathWorks this behavior as a bug?

  2 Comments

Or you can give a small simple example here, to illustrate it.
dami's "Answer" moved here since it's a reply to me rather than a solution to the original posting.
Here you can find an example, I'm stuck for days, I cannot even find a workaround.

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