An n by m matrix of (0,1) indicator variables,
where n is the length of classification and m is
the number of unique values or symbols in classification.
Columns are labeled by the unique values in classification,
and the [i,j]th entry is 1 if classification[i]
is the jth unique value or symbol in sorted order
classification.
If a noise value of symbol is designated, the corresponding indicator
variables are relocated to the last column of the matrix.