The nominal and ordinal array data types might be removed in a future release. To represent ordered and unordered discrete, nonnumeric data, use the MATLAB® categorical data type instead.
c = cat(dim,A,B,...)
c = cat(dim,A,B,...) concatenates the categorical arrays A,B,... along dimension dim. All inputs must have the same size except along dimension dim. The set of categorical levels for C is the sorted union of the sets of levels of the inputs, as determined by their labels.