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 = int8(A)
B = int8(A) converts the categorical array A to a signed 8-bit integer array. 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. If A contains more than intmax('int8') levels, the internal codes will saturate to intmax('int8') when cast to int8.