MATLAB: Grpstats flexibility for additional functions

Question

Hi, I am just wondering if the grpstats function can be used with things other than the standard formulas listed on the help page. A perfect example would be if I wanted population standard deviation instead of the canned sample standard deviation. This would then extend to personally written functions as well.

Grpstats appears to be an extremely useful function for statistical analysis if it is indeed more flexible than what I'm see in the help file.

Any advice or alternative recommendations for calculating statistics by group would be greatly appreciated.

Thanks much, Brian

Answer 1

If you look at the documentation the input variable whichstats can be a function handle. So for your example of the population standard deviation we can do the following:

x = rand(50,1); % Make some random data.
grpVar = logical([ones(25,1);zeros(25,1)]); % Split data into 2 groups
popStd = @(y) std(y,1); % make a function handle that computer pop. std.
myStats = grpstats(x,grpVar,popStd);

Using this method, you can make your own statistical functions. Also the list of stats given in the doc is not exhaustive. For example:

myKurt = grpstats(x,grpVar,'kurtosis');

returns the kurtosis of the groups.