The function 'polarhistogram' can produce overlapping bins
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Alexandre Aksenov
on 11 Jan 2022
Edited: Alexandre Aksenov
on 18 Sep 2022
Good day
I am experiencing an unexpected behavior of the function 'polarhistogram'. Here is my code:
thetaEx = [0.1 1.1 5.4 3.4 2.3 4.5 3.2 3.4 5.6 2.3 2.1 3.5 0.6 6.1];
%see https://www.mathworks.com/help/matlab/ref/polarhistogram.html
figure('Name','Plausible histogram');
polarhist1 = polarhistogram(thetaEx);
Edges1 = polarhist1.BinEdges; %-> (0:2*pi/3:2*pi) : 1x4 double
figure('Name','histogram with intersecting bins');
polarhist2 = polarhistogram(thetaEx+2*pi/3);
Edges2 = polarhist2.BinEdges; %-> (pi/2:3*pi/4:(2*pi+3*pi/4)) : 1x4 double
Overlap2 = Edges2(end)-Edges2(1)-2*pi; %-> pi/4
%These numbers confirm an overlap.
figure('Name','histogram made plausible');
polarhist3 = polarhistogram(mod(thetaEx+2*pi/3,2*pi));
Edges3 = polarhist3.BinEdges; %equals Edges1
Here are the figures.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/859195/image.jpeg)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/859200/image.jpeg)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/859205/image.jpeg)
The bins of the second histogram are clearly overlapping, which is confirmed by the property 'BinEdges'. This is not what one would expect of a histogram.
The third histogram shows that this unexpected behavior varies depending on shifts by multiples of 2*pi, although this transformation does not modify an angular distribution.
Could one indicate whether I am missing a necessary condition for using the function, or another important detail?
Thanks in advance,
Alexandre
The version of Matlab used: R2021b
Edit
The second histogram changes when the same code is run in Matlab R2022b. The new edges contain no overlap:
Edges2 = polarhist2.BinEdges; %R2022b: 2*pi/3:2*pi/3:8*pi/3
The new figure is a correct histogram, looking as follows:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1128425/image.jpeg)
5 Comments
Adam Danz
on 17 Jan 2022
I can't imagine a circumstance where wrapped radians to [0,2pi] would cause a problem since the range of radians in a polar plot are the same interval, [0,2pi].
You could contact tech support to report this issue. If they provide a better workaround or explain why this is not a bug, please share their feedback.
Accepted Answer
Shivam Singh
on 4 Feb 2022
Hello,
It is my understanding that you are facing the issue of overlapping bins in some cases when you are using the “polarhistogram” function.
This issue is brought to the notice of our developers and they may be investigating further.
thetaEx = [0.1 1.1 5.4 3.4 2.3 4.5 3.2 3.4 5.6 2.3 2.1 3.5 0.6 6.1];
%see https://www.mathworks.com/help/matlab/ref/polarhistogram.html
figure('Name','Plausible histogram');
polarhist1 = polarhistogram(thetaEx);
Edges1 = polarhist1.BinEdges; %-> (0:2*pi/3:2*pi) : 1x4 double
figure('Name','histogram with intersecting bins');
polarhist2 = polarhistogram(mod(thetaEx+2*pi/3,2*pi));% THIS LINE IS ONLY MODIFIED FROM YOUR CODE
Edges2 = polarhist2.BinEdges; %-> (pi/2:3*pi/4:(2*pi+3*pi/4)) : 1x4 double
Overlap2 = Edges2(end)-Edges2(1)-2*pi; %-> pi/4
%These numbers confirm an overlap.
figure('Name','histogram made plausible');
polarhist3 = polarhistogram(mod(thetaEx+2*pi/3,2*pi));
Edges3 = polarhist3.BinEdges; %equals Edges1
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