# Is there a better way to plot categorical data radially than using the polarhistogram function?

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Austin M. Weber el 15 de En. de 2024
Editada: Austin M. Weber el 1 de Feb. de 2024
It is easy to plot categorical data with the histogram function:
figure
histogram(authors,DisplayOrder='descend',Normalization='probability')
But, this does not work if you try to plot the data radially using polarhistogram, which requires that the data be numeric or logical. It is simple enough to get the number of counts for each cateogory in the categorical data by using the histcounts function, but plugging the numeric data directly into polarhistogram will not treat the numbers as discrete values. Instead, the function will automatically bin the data like this:
num_authors=histcounts(authors);
figure
polarhistogram(num_authors)
I have found a convoluted workaround in which you can specify the number of bins that you want the data to be divided into, but this is a pain because you have to define the widths of the bins in radians and the distance between tick marks in degrees:
% Get a list of all the category names
author_cats = categories(authors);
% Define number of bins
nbins = length(author_cats);
% Define widths of the bins (in radians)
% Define position of tick marks for adding categorical labels (in degrees)
center_bin_positions = (360/nbins) / 2;
bintickpositions = center_bin_positions : center_bin_positions *2 : 360 - center_bin_positions;
% Create plot
figure
h = polarhistogram('BinEdges',binwidths,'BinCounts',num_authors);
ax = gca;
% Normalize inner cicular tick marks as percentages
h.Normalization = 'percentage';
ax.RTickLabel = string(ax.RTickLabel) + '%';
thetaticks(bintickpositions)
thetaticklabels(author_cats)
for i = 1:nbins
value = sprintf('%0.1f',h.Values(i));
ax.ThetaTickLabel{i} = string(ax.ThetaTickLabel{i}) + ' (' + value + ' %)';
end
While this seems to work okay, making further customizations to the plot only makes things more complicated. For instance, I would prefer to plot the categorical data in descending order so that everything can be more easily compared.
Is there a better way to produce plots like this in MATLAB?
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Mario Malic el 16 de En. de 2024
What's wrong with histogram, you can adjust the looks of it, make bins wider and align text to be perpendicular to the X axis which should look just fine. Polar charts are a little bit complicated, maybe I would suggest to do it in Excel if you insist on that.
Austin M. Weber el 16 de En. de 2024
Editada: Austin M. Weber el 16 de En. de 2024
The histogram function is great, but if your categorical data has a lot of categories it becomes almost impossible to read them on the x-axis. Radial (polar) histograms are a much better option for large categorical datasets. Here are a couple of great examples:

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Ravi el 1 de Feb. de 2024
Hi Austin M Weber,
Unfortunately, there is no direct option available in the “polarhistogram” function to arrange the bins in ascending or descending order. Instead, you can use the “radialhistogram” function provided in the attached file exchange link to plot the histogram in desired way.
Example on how to use the function:
2. Let us assume six programming languages “C”, “C++”, “Java”, “MATLAB”, “Python”, “C#” as categories.
3. Let the count be the number of students using the languages in a class of 200 students.
4. Please note that the “radialhistogram” function requires the data to be categorical.
% Generate a sample data
cat = categorical({'C', 'C++', 'Java', 'MATLAB', 'Python', 'C#'});
data = repelem(cat, [60, 15, 34, 45, 20, 26]);
tabulate(data);
Value Count Percent C 60 30.00% C# 26 13.00% C++ 15 7.50% Java 34 17.00% MATLAB 45 22.50% Python 20 10.00%
% To sort the data in descending order,
% specify 'descend' as the second argument.
We can observe that the bins are in descending in anti-clockwise order.
Thanks,
Ravi
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Austin M. Weber el 1 de Feb. de 2024
Editada: Austin M. Weber el 1 de Feb. de 2024
@Ravi, the radialhistogram function is actually my own File Exchange submission. After I realized that there wasn't a simple way of making radial histograms in MATLAB I decided to go ahead and spend a few hours writing a function for it.
That said, I forgot to share the function on this MATLAB Answers forum, so thank you for doing it for me! I went ahead and accepted your answer.

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