MS Excel: Finding the earliest date on a row of mixed content - vba

Question

Does anyone know how to get the earliest date on a row in Microsoft Excel. There is not a predictable number of columns on each row, and there are values other than dates which need to be ignored. It could be done with Excel formulas or VBA.
Does anyone have any suggestions?
Right now I am using this quick and dirty VBA function, but when I loaded new input data (approx 200 rows by 100 columns) a message box came up saying that Excel does not have enough resources to process my changes.
' returns smallest date on row
Public Function getSmallestDateFromRow(r As Integer, sheetName As String) As Date
Dim toReturn As Date
Dim rng As Range
Dim scanToColumn As Integer
Dim c As Integer
Dim tmp As Variant
Set rng = Sheets(sheetName).Cells.Find("*", [a1], , , xlByColumns, xlPrevious) 'is this inefficient?
scanToColumn = rng.Column
toReturn = #12/12/2100#
For c = 1 To scanToColumn
tmp = Sheets(sheetName).Cells(r, c).Value
If (IsDate(tmp)) Then
If (toReturn = Null) Then
toReturn = tmp
ElseIf (toReturn > tmp) Then
toReturn = tmp
End If
End If
Next c
If (toReturn = #12/12/2100#) Then
toReturn = 0
End If
getSmallestDateFromRow = toReturn
End Function

Answer 1

You have to remember that Excel (and many other Microsoft products) store dates as floating-point numbers:
The integer part is the count of days elapsed since January 1st, 1900 (e.g.: 1 is equivalent to 1/1/1900)
The decimal part is the 'fraction' of day elapsed (e.g.: 0.5 is equivalent to 12:00 pm)
The question on how to find a minimum or maximum date value is then obfuscated by the fact that you may have many other numbers in your row. So you have to define first a "valid rank" for the dates. After that, a simple "array formula" can do the trick:
Example. Let's say your valid range is between January 1st, 2000 and December 31st, 2100. Then your valid "number rank" is:
1/1/2000 is equivalent to 36526
12/31/2100 is equivalent to 73415
Now you can write the function to track the minimum date value within this range:
function trackMinimum(rowRange as range) as date
on error resume next
dim j as integer, minValue as date
dim t0 as double, t1 as double
dim ans as date
t0 = cdbl(dateserial(2000,1,1))
t1 = cdbl(dateserial(2100,12,31))
ans = 0
for j = 1 to rowRange.columns.count
if ans = 0 then ' You need to store the first valid value
if rowRange.cells(1,j).value >= t0 and rowRange.cells(1,j) <= t1 then
ans = rowRange.cells(1,j).value
end if
else
if (rowRange.cells(1,j).value >= t0 and rowRange.cells(1,j) <= t1) _
and rowRange.cells.value < ans then
ans = rowRange.cells(1,j).value
end if
end if
next j
trackMinimum = ans
end function
Of course I am assuming that the rowRange parameter is a single row range.
Hope this helps you
By the way, the isDate() function is not "fail safe": It must take a valid expression (text) to detect if it is a date or not, and that may depend on formatting. That said, you may prefer to use isDate(.cells(r,c).Text)' instead of.value, since theValue` property may return a double or floating-point value that can be evaluated as "not a date".