how do I add MEAN to Boxplot?

I am thinking about locating MEAN as a straight horizontal line or a symbol inside the boxplots for illustration purposes. I would say it is possible since distributions are not significantly skewed. Any suggestions?!

Here is a MATLAB sample code:

rng default  % For reproducibility
x1 = normrnd(5,1,100,1);
x2 = normrnd(6,1,100,1);
figure
boxplot([x1,x2],'Notch','on','Labels',{'mu = 5','mu = 6'})
title('Compare Random Data from Different Distributions')

cust_colr = [0, 0.5, 1
    0.60156, 0.80078, 0.19531
    0.5, 0, 0];

h = findobj(gca,'Tag','Box');
 for j=1:length(h)
     patch(get(h(j),'XData'),get(h(j),'YData'),cust_colr(j,:));
 end

Output picture is shown below:

Answer 1

[michio]

The ability to plot the mean values using boxplot is not available as of release R2016b. To work around this issue, you can find these values and plot them manually. The example below shows how to plot the mean value of each group:

 % Generate random data
 X = rand(10);

 % Create a new figure and draw a box plot
 figure;
 boxplot(X)

 % Overlay the mean as green diamonds
 hold on
 plot(mean(X), 'dg')
 hold off

[Mohammed]

Thanks for your answer! If MATLAB plot command is a 2-D function, do you know how it retrieves the x-axis values in this scenario?!

[michio]

You are welcome. I am not so sure what you mean by "how to retrieve the x-axis values". What values are you referring to?

[Mohammed]

If MATLAB plot command is a 2-D function, don't you think we need pair of values to plot green diamonds? In your case, you just plot them with one value.

[michio]

I see. If you look at the documentation page of plot function, for example, it states

"plot(Y) creates a 2-D line plot of the data in Y versus the index of each value. If Y is a vector, then the x-axis scale ranges from 1 to length(Y)."

So 2D function does accept only one value and its x-values is going to be just the index of each value. Hope it answers your concern.

[Mohammed]

You did well. That's what I anticipated. Thanks again!

[michio]

Glad it helped;)

[JIAYING WU]

but the means do includes outliers if there are any?

[Bárbara Antonucci]

Is functionally. Very great!

Answer 2

[Camilo Cárdenas]

Hi, thank you for your post.

I have got a question:

What aboout, if you have more than one box in a Diagramm? How can you assingn it to each group of data?

Thanks!

[Simon Diaz]

Hi, try to

% Generate random data
 X = rand(10,4);

 % Create names of each group
 names = {'name1','name2','name3','name4'};
 
 % Create a new figure and draw a box plot
 figure;
 boxplot(X,'Labels',names)
 % Overlay the mean as green diamonds
 hold on
 plot(1:length(X(1,:)),mean(X), 'dg')  % x-axis is the intergers of position
 hold off

[JB676]

mu_T = % set of values for category 1
mu_RN = % set of values for category 2
mu_T_RN, grp_T_RN = % combined dataset values and labels
hb = boxplot(mu_T_RN,grp_T_RN,'whisker',1);
% replace median with mean value
set(hb(6,1),'ydata',[mean(mu_T) mean(mu_T)]);
set(hb(6,2),'ydata',[mean(mu_RN) mean(mu_RN)]);

Get the handle to the boxplot, then adjust item 6 'ydata'. For a two category example: