That depends on what a "group" is. If it is a group of records, you can perform a find for that individual and get ( FoundCOunt ) will return the count you want. If you have a relationship to such a group of records so that only the individual you want to count is a member of the related records, then the count function can be used.
If you have many such individuals and you want a count for each, you can sort your records to group them by individual and then a "count of" summary field placed inside a sub summary layout part can give you the count.
But all of these assume that each "individual" is an individual record. If your group of individuals is some other kind of group then you'll need to tell us that.
Thank you for your help. What I need is - Each record contains an unique, individual ID. An individual ID may show up numerous times under each department. (Many departments within a company.) I would like to count the number of different IDs in each department. Not how many times one ID showed up.
Each record contains an unique, individual ID. An individual ID may show up numerous times under each department. (Many departments within a company.)
I'm afraid that you have a contradiction there. (English can be so imprecise.) If an Id may show up numerous times, it cannot be unique--at least to that table of records though it may be a unique identifier for records in a related parent table.
The best way to do what you want depends on what version of FileMaker you are using.
With FileMaker 11 and older, the "sum the reciprocal" method may be used: A new way to count unique values in FileMaker 12
With FileMaker 12 you also have the option to place a large, multi-line sized field on your layout that uses the ExecuteSQL function to list and count unique values: A new way to count unique values in FileMaker 12