categorical.ismatrix
categorical: TF = ismatrix (C)
Return true if categorical array is a 2-D array.
TF = ismatrix (C) returns a logical scalar TF,
which is true, if the categorical array C is a matrix, and
false otherwise. A matrix is an array of any type where
ndims (X) == 2 and for which size (X) returns
[H, W] with non-negative H and W.
Source Code: categorical