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Display mean of data on a boxchart

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Behzad Navidi
Behzad Navidi on 5 Apr 2020
Commented: dpb on 9 Apr 2020
I need to show the mean of each box plot on the figure. here is the code to generate my box plot:
x = 1:numel(data);
colors = rand(numel(data), 3);
figure();
ax = axes();
hold(ax);
for i=1:numel(data)
boxchart(x(i)*ones(size(data{i})), data{i},'MarkerStyle','none', ...
'BoxFaceColor', colors(i,:), ...
'LineWidth', 0.5, ...
'WhiskerLineStyle', '-')
end
set(gca,'xtick',[])
When I had just one boxplot I simply used this line:
hold on
plot(mean(x), '*')
But here when I use it in the code:
x = 1:numel(data);
colors = rand(numel(data), 3);
figure();
ax = axes();
hold(ax);
for i=1:numel(data)
boxchart(x(i)*ones(size(data{i})), data{i},'MarkerStyle','none', ...
'BoxFaceColor', colors(i,:), ...
'LineWidth', 0.5, ...
'WhiskerLineStyle', '-')
plot(mean(data{i}), '*') %%%%%%%%%%<<<<<<<<<<<<< HERE
end
set(gca,'xtick',[])
It shows all mean values on the first boxplot only, meanwhile I need to have one * as a mean value for each boxplot.
Best Regards

  2 Comments

dpb
dpb on 5 Apr 2020
>> which -all boxchart
'boxchart' not found.
>>
??? There's a boxplot, no info on boxchart

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Accepted Answer

dpb
dpb on 5 Apr 2020
"??? There's a boxplot, no info on boxchart"
Well, bless their little pea-pickin' hearts but TMW has done it again...introduced yet another duplicated function with different name and slightly different syntax/characteristics. I wish they would quit doing that and do something really new and different like introduce a hatching pattern or something instead...
Anyways my rant aside, looks like you're going at this the hard way. Reading between the lines, it looks like you have a cell array of numel() elements and you're iterating over it to plot each cell separately.
Instead
figure;
y=cellmat(data); % convert the cell array to matrix
hBx=boxchart(y,'MarkerStyle','none', ... % do the box plot
'BoxFaceColor', colors(i,:), ...
'LineWidth', 0.5, ...
'WhiskerLineStyle', '-');
hold on
hLmn=plot(1:size(y,2),mean(y), '*','r'); % and the stars for means
hAx=gca;
hAx.XTick=[];
Only two caveats:
  1. each element in data is same number points; if this isn't so, will need to augment the shorter cells to length of longest with NaN, and
  2. the data in each cell are column vectors--if rows, then transpose the y array before calling boxchart
You can stick with the existing way of generating an unneeded x variable to fake out barchart by giving an artificial grouping variable, but that's kinda' messy way. If they were going to write a new one, don't know why didn't allow for an x axis variable while at it other than simply the only grouping variable option.
N=numel(data);
colors = rand(N, 3);
figure;
hAx = axes();
hold on
for i=1:N
boxchart(i*ones(size(data{i})), data{i},'MarkerStyle','none', ...
'BoxFaceColor', colors(i,:), ...
'LineWidth', 0.5, ...
'WhiskerLineStyle', '-')
plot(i,mean(data{i}),'*r') % you didn't put in an x coordinate so all plotted at 1,mean(y)
end
set(gca,'xtick',[])
I'd recommend looking at vectorizing instead of the latter, though...

  3 Comments

Behzad Navidi
Behzad Navidi on 6 Apr 2020
Thank you for your precious advices.
Best regards
Guillaume Le Goc
Guillaume Le Goc on 9 Apr 2020
I don't think you can achieve having different colors for each boxes without a loop.
dpb
dpb on 9 Apr 2020
Hmmm....that looks to be so, unfortunately. I was presuming there would be a CData property as there is in bar that could be set but no, they didn't seem to consider that in the design process. Does make one wonder how TMW does come up with the things they do/don't include and the lack of consistency across functions is maddening.

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