Here’s a puzzle for you. A set, depending on filters, may have anywhere between 1 and 100 members. If there are more than 5 members, we should see 4 with an aggregated “Other” member. If there are 5 or fewer we should just see them.

We could try to do it with an insane combination of head and topCount and pull end up pulling out far too much hair. Instead, Cognos has a couple built in function that makes this a snap.

_firstFromSet is a function that will return the first N members from a set, with an optional overflow. Let’s say that Product Line has 5 members: Camping Equipment, Golf Equipment, Mountaineering Equipment, Outdoor Protection, and Personal Accessories. If we were to do _firstFromSet([Product Line],4,1) it would return all 5 members. Order Method, on the other hand, has 7 members. _firstFromSet([Order Method],4,1) will return only the first 4.

So this gives us either 4 or a max of 5 members, but how do we get that “Other” member? There is another, similar, function called _remainderSet. If the set in question contains more than a specified number of members, it will return a specified member. If the referenced set contains fewer, it will return an empty set. So let’s see an example:

_remainderSet (
  member(
      currentMeasure - total(currentMeasure within set _firstFromSet([Dim],4,1))
    , 'Other'
    , 'Other'
    , hierarchy([Dim])
  )
  , [Dim]
  , 5
)

So in this case, if [Dim] contains more than 5 members, it will create a calculated member that finds the total for the remaining members.

Putting it together we get:

  union(
  _firstFromSet (
     [Dim]
    , 4
    , 1
  )
  ,  _remainderSet (
    member(
        currentMeasure - total(currentMeasure within set _firstFromSet([Dim],4,1))
      , 'Other'
      , 'Other'
      , hierarchy([Dim])
    )
    , [Dim]
    , 5
  )
)

The report is, as usual, attached below.
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