How to do boxplot for vectors with different sizes

I have four vectors (A1, A2, A3, A4) which have different length, I am trying to generate boxplot for these data:

boxplot([A1, A2, A3, A4], 'notch', 'on', 'color', [0 0 0], 'outliersize',0, 'labels',{'data1', 'data2', 'data3', 'data4'});

but I have an error: Error in boxplot (line 286) [groupIndexByPoint,groupVisibleByPoint,labelIndexByGroup,gLevelsByGroup,...

Does anyone know what is wrong?

Answer 1

[Brendan Hamm]

You are passing in all of your data as one big long row vector (that is A1,...,A4 are all row vectors and you concatenate to a larger row vector with [A1,A2,A3,A4]), but boxplot treats different columns as different variables, or in the case of a row vector it will treat this as many observations from a single variable. This is fine (excepting that it does not have the results you want) but you then provide 4 labels and thus the error. For this reason you need to pass in a grouping variable as well, which will describe which group the data came from:

    G = [ones(size(A1))  2*ones(size(A2)) 3*ones(size(A2)) 4*ones(size(A2))];
    X = [A1, A2, A3, A4];
    boxplot(X,G,'notch','on','colors',[0 0 0],'symbol','','labels'{'data1','data2','data3','data4'});

Note, if you want to get rid of the outliers you want to set the symbol to the empty string as opposed to setting the outliersize to 0.

[Karolina]

Thank you, it works perfectly!

Below is the final code, because I've found two small mistakes in your code.

G = [ones(size(A1))  2*ones(size(A3)) 3*ones(size(A4)) 4*ones(size(A4))];
X = [A1, A2, A3, A4];
boxplot(X,G,'notch','on','colors',[0 0 0],'symbol','','labels',{'data1','data2','data3','data4'});

[Brendan Hamm]

Ah yes! Copy and paste can be a killer. Glad you caught it!

Answer 2

[Foroogh Hajiseyedjavadi]

Thanks, @Brendan Hamm for the help. I had a large dataset and the method you posted worked great, just needed to work on it a bit to make it more generic for a large data. I share this code based on your help, in case anyone else is dealing with a large dataset like me. hope it helps!:)

grp=[]; %grouping matrix
for n=1:45
  grp=vertcat(grp,n*ones(sizes(n),1));%sizes is a variable with n column each column stores the size of each variable
end
figure();
boxplot(cell2mat(speeddata(~cellfun(@isempty,speeddata))),grp)%speeddata is a cell array with 45 columns of data, each column with different size