yields a conjunctive vector of classes identified within strings
[obtained_classes, name_classes, size_classes] = str2conj(string_id,startpos,endpos);
the identifier of the observations, a string vector of dimension n
the first and last characters within string_id which define a name used as a class identifier
a conjunctive vector of dimension n which contains the integers: 1, 2, ...nclasses where nclasses is the number of the different classes
the name of the classes extracted from string_id; a string vector of dimensions (nclasses X 1)
the number of observations in each group; an integer vector of dimensions (nclasses X 1)