The command selects the indexes of the data records to a new class. It evaluates a given boolean expression for each records, and the records fulfilling the value TRUE are collected to the class. Therefore, the expression must return boolean values. See more about expressions in Section 4.2.1.
Example (ex4.5): The indexes of the data records which have larger values than 3.0 for the field "zn" are put to the class "bigZn".
NDA> load boston.dat NDA> selcl -cout cld1 -clout bigZn -expr 'boston.zn' > 3.0; -v ...