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.
B = uint64(A)
B = uint64(A) converts the categorical array A to unsigned 64-bit integers. Each element of B contains the internal categorical level code for the corresponding element of A.
Undefined elements of A are assigned the value 0 in B.