How to interpolate zero cells in a large excel sheet? - excel

Question

I have a long excel file which contains numbers collected from a website. Less than 1% of the cells contain zero due to an error from the source. Therefore, I want to find update those cells and interpolate them with the nearest values. The length of the zero cells is some time single, hence I can simply take the average of the nearest non-zero values. However, a few places it is longer than one, hence I need to use linear interpolation.
Sample extracted data
+---+------+------+------+------+------+------+------+------+---+---+---+---+---+---+---+---+------+------+------+------+------+------+------+------+------+
| | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y |
+---+------+------+------+------+------+------+------+------+---+---+---+---+---+---+---+---+------+------+------+------+------+------+------+------+------+
| 1 | 4058 | 4048 | 4049 | 4082 | 4090 | 4115 | 4118 | 4109 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3990 | 4058 | 4064 | 4053 | 4057 | 4093 | 4123 | 4137 | 4133 |
+---+------+------+------+------+------+------+------+------+---+---+---+---+---+---+---+---+------+------+------+------+------+------+------+------+------+

Answer 1

Here's a very general script that might do something like that. It is only tested on positive values and ten rows, so you will definitely need to adapt it to many corner cases - but it should point you in the right direction:
Sub Interpolate()
Dim valueToTop As Integer
For Row = 1 To 10
valueToTop = -1
valueToBottom = -1
If Cells(Row, 1).Value = 0 Then
RowToTop = Row - 1
Do While RowToTop > 0
If Cells(RowToTop, 1).Value > 0 Then
valueToTop = Cells(RowToTop, 1)
Exit Do
End If
RowToTop = RowToTop - 1
Loop
Debug.Print valueToTop
Debug.Print RowToTop
RowToBottom = Row + 1
Do While RowToBottom > 0
If Cells(RowToBottom, 1).Value > 0 Then
valueToBottom = Cells(RowToBottom, 1)
Exit Do
End If
RowToBottom = RowToBottom + 1
Loop
Debug.Print valueToBottom
Debug.Print RowToBottom
Cells(Row, 2).Value = valueToTop + (Row - RowToTop) * (valueToBottom - valueToTop) / (RowToBottom - RowToTop)
End If
Next Row
End Sub