Autofill error on Range Class - vba

Question

I'm trying to add 2 columns with formulas and autofill down to the last row, but I'm getting an
Autofill method of range class failed
when running the code. It breaks at the line that starts with Activecell.Autofill
Sub addColumnsandChange()
Dim LastRow As Integer
'Finds the value of the last row
LastRow = ActiveSheet.Range("A" & Rows.Count).End(xlUp).Row
Selection.EntireColumn.Insert
Selection.EntireColumn.Insert
ActiveCell.FormulaR1C1 = "YoY% Change"
ActiveCell.Offset(0, 1).Range("A1").Select
ActiveCell.FormulaR1C1 = "3 Year CAGR"
ActiveCell.Offset(1, -1).Range("A1").Select
ActiveCell.FormulaR1C1 = "=IFERROR((RC[-1]-RC[2])/RC[2],"""")"
ActiveCell.Offset(0, 1).Range("A1").Select
ActiveCell.FormulaR1C1 = "=IFERROR((RC[-2]/RC[2])^(1/3)-1,"""")"
ActiveCell.Offset(0, -1).Range("A1:B1").Select
ActiveCell.AutoFill Range("A1:B" & LastRow), Type:=xlFillDefault
Range("A1:B" & LastRow).Select
End Sub
Since incorporating the LastRow variable I have not been able to run the code.
Instead it returns a run-time error
Autofill method of range class failed
when debugging. How should I autofill and end the code?

Answer 1

While it is unclear on where you actually start (e.g. what cell Selection is), I suppose that it could be assumed that you know what you are doing before running the sub procedure. In any event, it is better to .FillDown or simply write the formulas all at once.
Using .FillDown:
Sub addColumnsandChange()
Dim lastRow As Long
'Finds the value of the last row
lastRow = ActiveSheet.Range("A" & Rows.Count).End(xlUp).Row
With Selection.Cells(1)
.Resize(lastRow, 2).EntireColumn.Insert
.Offset(0, -2).Resize(1, 2) = Array("YoY% Change", "3 Year CAGR")
.Offset(1, -2).FormulaR1C1 = "=IFERROR((RC[-1]-RC[2])/RC[2], TEXT(,))"
.Offset(1, -1).FormulaR1C1 = "=IFERROR((RC[-2]/RC[2])^(1/3)-1, TEXT(,))"
.Offset(1, -2).Resize(lastRow - 1, 2).FillDown
.Offset(0, -2).Resize(lastRow, 2).Select
End With
End Sub
Writing all formulas at once:
Sub addColumnsandChange()
Dim lastRow As Long
'Finds the value of the last row
lastRow = ActiveSheet.Range("A" & Rows.Count).End(xlUp).Row
With Selection.Cells(1)
.Resize(lastRow, 2).EntireColumn.Insert
.Offset(0, -2).Resize(1, 2) = Array("YoY% Change", "3 Year CAGR")
.Offset(1, -2).Resize(lastRow - 1, 2).FormulaR1C1 = "=IFERROR((RC[-1]-RC[2])/RC[2], TEXT(,))"
.Offset(1, -1).Resize(lastRow - 1, 2).FormulaR1C1 = "=IFERROR((RC[-2]/RC[2])^(1/3)-1, TEXT(,))"
.Offset(0, -2).Resize(lastRow, 2).Select
End With
End Sub

Answer 2

You are trying to autofill starting with the first row.
However, the formulas you are trying to copy are on the second row. Your first row contains header text.
Please note: You don't have to Select a cell before changing it's value. Your code would perform much faster if you would leave our those Selects. (And the code would become much easier to read and understand)