classInds = classNamesToClassInd(dataSet,classNames)
    Return the class indices corresponding to the classes
    specified in the character array or cell of strings,
    classNames.
 
    Note that the classInd is not necessarily the same as the
    target value.
 
   ds = prtDataGenIris;
   ds.classNamesToClassInd('Iris-setosa'); %Setosa is the first