The map tool can perform an index mapping in which multiple elements of informant X are mapped to the same element of informant Y. To aggregate multiple elements into one, the map tool sums the values of the composite elements. However, there may be a need to use a different aggregation function such as minimum, maximum, or average.

The following example demonstrates how to implement this logic.

In this example, the a variable indexed by the informant unitID will be mapped to a variable indexed by the informant plantID. The contents of these informants are:

plantID[]: set
 version: 3
 desc:    localinformant plantID[] = create (; object=set, data="Plant1 Plant2")
 data:    2 elements
-----------------------------------
1     Plant1          
2     Plant2          

unitID[]: set
 version: 3
 desc:    localinformant unitID[] = create (; object=set, data="Unit1 Unit2 Unit3 Unit4 Unit5")
 data:    5 elements
-----------------------------------
1     Unit1           
2     Unit2           
3     Unit3           
4     Unit4           
5     Unit5           

The variable unitComYr contains commissioning years by unitID

1. Create the following desired mapping from unitID to plantID is:
   

Unit1 → Plant1
Unit2 → Plant2
Unit3 → Plant1
Unit4 → Plant1
Unit5 → Plant2

local unitToPlantMap[uid] = create (; dataType=integer, dim=unitID, data="1 2 1 1 2")

1. Create a mask that will expand unitComYr to include plantID

local pid[pid,pid] = diag (1.0; dim=plantID)
local plantIDMask[uid,pid] = boolne (dimtran (pid[pid,pid]; map1=unitToPlantMap[uid], newDims=1, checkData=off),0)

local unitComYrx[uid,pid] = unitComYr[uid] * plantIDMask[uid,pid]

! add offset to remove 0's before taking minimum
local unitComYry[uid,pid] = booleq (unitComYrx[uid,pid],0) * 9999 + unitComYrx[uid,pid]

! variable that contains online date, which is the earliest commissioning year of the units that comprise the plant, by plant id
local plantOnlineDate[pid] = coordmin (reorder (unitComYry[uid,pid]; plantID, unitID); numDims=1)
table (plantOnlineDate[pid])