SETPROP Add property to data set

    DATA=SETPROP(DATA,PROP,VAL)
    DATA=SETPROP(DATA,PROP,VAL,'feat')
    DATA=SETPROP(DATA,PROP,VAL,'data')

 INPUT
    DATA     Data set
    PROP     property name
    VAL      property value

 OUTPUT
    DATA     Data set

 DESCRIPTION
 SETPROP sets into data set DATA a property called PROP with value VAL.
 Without extra argument, SETPROP sets sample property which must contain
 one entry for each data sample. SETPROP may also set feature properties
 with one entry per feature and data properties without restriction.

 SEE ALSO
 GETPROP, GETPROPLIST