need expression help for nth match with restrictions

[#1]

Hi,  trying to craft an expression to get a result into a chart table.

I have a data table listing arrival times for vehicles to incidents (the attached qvw illustrates).  Each vehicle has a type Pumper, Ladder or Rescue.  I need to determine when benchmark X has been met.  Benchmark X is the first time when three pumpers have arrived OR two pumpers and one ladder have arrived.

Struggling. I can get the three pumpers part in isolation, I use the "firstsortedvalue" function and 3 as the third parameter filtering on type.  The second part is tricky and I can't think of how to start.

[swuehl]

Maybe you could create a field which holds a composite of arrival time for all pumpers and for the first ladder per incident.

Like:

TMP:

LOAD FirstSortedValue(RowID, ArrivalTime) as RowID, FirstSortedValue(ArrivalTime,ArrivalTime) as PL resident Arrival where Type = 'Ladder' group by Incident;

LOAD RowID, ArrivalTime as PL Resident Arrival where Type='Pumper';

Result:

left join (Arrival) LOAD * Resident TMP;

drop table TMP;

Then do your firstsortedvalue(PL,PL,3) in the chart.

see also attached,

Stefan

P.S. This is not selection sensitive.