Excel Array formula using INDEX and is variable dependant

Question

I currently have a sheet where data is being entered into specific columns. Then within a summary sheet, I am using an array formula with an index to generate a list of all data on the original sheet matching a specific field.

Each column on the summary sheet has an array formula, linking back to the equivalent column on the data sheet. A->A, B->B, C->C etc...

The array formula is as follows:

{=IFERROR(INDEX('data'!C$2:C$1168,SMALL(IF('data'!$S$2:$S$1168>='OUTPUT'!$A$2,ROW('data'!C$2:C$1168)-ROW('data'!C$2)+1),ROWS('data'!C$2:'data'!C2))),"")}

This formula works perfectly and generates a live updating list of all rows where the value of cell column "S", in sheet "data", is "OUTPUT".

Sheet "data":

|Sample A|Result A|OUTPUT|
|Sample B|Result B|0     |
|Sample C|Result C|OUTPUT|

Result on the "summary" sheet:

|Sample A|Result A|
|Sample C|Result C|

Within the sheet "data" however, there is now also a column for quantity, and I would like to attempt to have that reflected in the "summary" sheet. As follows:

Sheet "data":

|Sample A|Result A|OUTPUT|  2  |
|Sample B|Result B|0     |  5  |
|Sample C|Result C|OUTPUT|  3  |

Result on the "summary" sheet:

|Sample A|Result A|
|Sample A|Result A|
|Sample C|Result C|
|Sample C|Result C|
|Sample C|Result C|

Any advice or recommendations on how to cause this "loop" with an array would be much appreciated. I would typically write a macro to handle the data with a function that loops the output whenever needed, however my objective is to avoid having to run a macro each time new data is added.

Thank you and regards

Answer 1

Excel formulas are nice, but I tend to use UDFs in conjunction with Named Ranges in this situation.

Use a UDF to return an array of all the desired out strings ONCE, and put into a Named Range. Then call INDEX on your named range.

UDF:

Public Function getResultArray( _
       sampleRange As Range, _
       isOutputRange As Range, _
       QuantityRange As Range, _
       str as string) As String()

  'error handling for inputs here
  Dim totalQuantity As Long
  totalQuantity = Application.WorksheetFunction.SumIf(isOutputRange, str, QuantityRange)

  Dim retArr() As String
  ReDim retArr(1 To totalQuantity)

  Dim ioArr As Variant, qArr As Variant, sampleArr As Variant
  ioArr = isOutputRange.Value
  qArr = QuantityRange.Value
  sampleArr = sampleRange.Value

  Dim i As Long, j As Long, counter as Long
  For i = LBound(ioArr) To UBound(ioArr)
        If ioArr(i, 1) = str Then
              For j = 1 To qArr(i, 1)
                    counter = counter + 1
                    retArr(counter) = sampleArr(i, 1)
              Next j
        End If
  Next i

  getResultArray = retArr
End Function

Named Range:

ResultArray = getResultArray(data!$A$2:$A$4, data!$C$2:$C$4, data!$D$2:$D$4, OUTPUT!$A$2)

Where you want the 'summary':

=INDEX(ResultArray, ROWS('data'!C$2:'data'!C2))

This cuts down on workbook calculation, as the arrays are only calculated once, and not for each worksheet formula(array formulas are expensive)