How to remove duplicate entries in a cell array (when those entries are 2x2 matrices) (Matlab)

Question

Is there a nice function that will remove duplicate entries in a cell array?

Some googling threw up the function 'unique', but it appears that only works if all the entries of the array are strings. Mine are 2x2 matrices.

Thanks

Answer 1

I've used a combination of CELLFUN, CELL2MAT and UNIQUE. The idea is to convert each matrix to a vector, convert those cell array to a matrix and apply unique, The result you can convert back to cell array with NUM2CELL.

x = {[1 2; 3 4], [1 2; 3 4], [5 6; 7 8], [1 2; 3 4], [5 6; 7 8]}';
x1 = cellfun(@(y)y(:)', x, 'UniformOutput',0);
x2 = cell2mat(x1);
x3 = unique(x2,'rows');
x4 = num2cell(x3,2);
x5 = cellfun(@(y) reshape(y,2,2), x4, 'UniformOutput',0);

Probably it can be done with less steps.

It's important to remember that this code will work only if all the cell array elements have the same size.

You can check for this condition with

assert(size(unique(cell2mat(cellfun(@size,x,'UniformOutput',0))),1) == 1,...
       'Cell elements have different size')