ISCLASS check if class is present in the data set

    T=ISCLASS(A,NAME)
    T=ISCLASS(A,{NAME1,NAME2,...})

 Check if there are only the given classes present:
    T=ISCLASS(A,{NAME1,NAME2,...},'only')

 INPUT
    A       Data set
    NAME    Class name (string)

 OUTPUT
    T       Logical value (1 if class with NAME is present in a.lab)

 DESCRIPTION
 ISCLASS implements a quick test if a class is present in the data set
 labels. If a cell array of strings is given, ISCLASS returns 1 only if
 all names in the cell array are present in A.lab.list.  ISCLASS also
 allows to check if the given classes are the only ones present using the
 extra 'only' flag.
 ISCLASS is a useful validation step at the beginning of a algorithm
 function which is assuming specific type of data sets.

 SEE ALSO
 SDALG