The operation matches the classified data <cldata2> to the classified data <cldata1>, and it replaces indexes in <cldata2> with the indexes of the classes of <cldata1>, from which the original indexes (the first occurrence) are found. The whole procedure is presented below, and a step for matching one index is described as a figure:
For each 
For each class 
For each 
If 
Then
Set 
in the target classified data to the class index 
Continue the next 
End
End
End
End
Example: See the example of the command joinind (Sect. 3.3).