Search code examples
matlabmeancell-array

Matlab: mean and stddev in a cell

In a single array it's pretty simple to get the mean or standard deviation (std) of its numbers, however in a cell, whose data doesn't have the same size in each of its positions I couldn't do mean2 or std2.

I know it's possible to do something if I copy all of the data in a single row or single column but I just wanted to ask if someone knows if there is a single formula to do it?

Thanks

Solution

  • You can use cellfun to compute per-cell mean and std:

    cell_mean = cellfun(@mean, my_cell);
cell_std = cellfun(@std, my_cell);

    For example:

    >> my_cell = {[1,2,3,6,8], [2,4,20]}
>> cellfun(@mean, my_cell)
ans =

4.0000    8.6667

>> cellfun(@std, my_cell)
ans =

2.9155    9.8658

    If you want the mean and/or std of all the elements in all the cells, you can:

    >> mean([my_cell{:}])
ans =

5.7500

>> std([my_cell{:}])
ans =

6.2048

    And, if your cell elements are all of different sizes, you can use cell2mat to assist you:

    >> mean(cell2mat(cellfun(@(x) x(:)', my_cell, 'uni', 0)))
ans =

5.7500

>> std(cell2mat(cellfun(@(x) x(:)', my_cell, 'uni', 0)))
ans =

6.2048