MATLAB: Sort boxplot based on 25-75th percentiles

boxplot

Hi all,

I have a figure with 3 boxplots in it (different colors each of them)

However, I would like to sort them based on the difference between 25th-75th percentile.

Is it possible to do it?

And if yes can I keep the initial colours after they have been sorted?

thanks a lot

NIkolas

Best Answer

Yes, it is possible. The algorithm would be something like

Find the percentiles on the data, using the prctile command, before plotting them with boxplot
Sort those percentiles, and store the sorting order
Use a grouping variable (the second argument to the boxplot command), making sure that the grouping variable values are sorted according to the correct order

I could probably give more specific advice if you upload the data and code that you are using now.

Related Solutions

MATLAB: How to extract the values of the data that constitute a certain percentile

The 'prctile' function does not provide an automatic way to extract the values of your data that constitute a certain percentile. However, you can use 'prctile' along with another couple lines of code to obtain these values. Below are a couple examples:

Method 1:

>> m = rand(1, 20); % generate a random list of numbers
>> percentiles = prctile(m, [10 20 30]); 
>> vals10 = m(m <= percentiles(1)); % values in the 10th percentile
>> vals20 = m(m <= percentiles(2)); % values in the 20th percentile
>> vals30 = m(m <= percentiles(3)); % values in the 30th percentiles

Method 2:

>> m = rand(1, 20);
>> mSorted = sort(m); 
>> vals10 = mSorted(1:floor(end * 0.1)); 
>> vals20 = mSorted(1:floor(end * 0.2));
>> vals30 = mSorted(1:floor(end * 0.3));

Note: Method 2 does not calculate the percentiles, just the values that constitute each percentile. It also does not keep the data in its original order.

MATLAB: How to pick the j-th percentile of a vector

If you don’t have the Statistics Toolbox, this doesn’t replicate the prctile results exactly, but it’s close:

pctl = @(v,p) interp1(linspace(0.5/length(v), 1-0.5/length(v), length(v))', sort(v), p*0.01, 'spline');

where v is the data vector and p is the percentile. You would call it as:

p = pctl(A, 25);

in your example.

Best Answer

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MATLAB: How to extract the values of the data that constitute a certain percentile

MATLAB: How to pick the j-th percentile of a vector

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