Thread: if there are two y-axis, how to set one of them to x-axis?

The force column is all zeros.

Were it not, you could interpolate time vs strain to get stress vs strain.

Firstly, the force column is not all zeros.

Look at column B, labeled "Force"

Check the file you uploaded; it only has data to row 565, and it's all zero.

Suggest you download the file you uploaded and look at it.

Weird.

Add this function to the workbook.

Code:

Private Sub dFrac(d As Double, r As Range, _
                  ByRef i As Long, ByRef dF As Double, _
                  iMatchType As Long)
    ' shg 1997-0606, 2009-0419
    '     2009-0604 added option for descending sort

    ' Returns an index to r in i and an interpolation fraction in dF
    ' r must be a 2+ element vector sorted a-/de-scending if iMatchType=1/-1

    If iMatchType = 1 And d <= r(1).Value2 Or _
       iMatchType = -1 And d >= r(1).Value2 Then
        i = 1
    Else
        i = WorksheetFunction.Match(d, r.Value2, iMatchType)
        If i = r.Count Then i = r.Count - 1
    End If

    dF = (d - r(i).Value2) / (r(i + 1).Value2 - r(i).Value2)
End Sub

Function LINTERP(x As Double, rX As Range, rY As Range) As Variant
    
    ' shg 1997-0606, 2009-0419
    '     2009-0604 added option for descending sort

    ' Linear interpolator / extrapolator
    ' Interpolates rX to return the value of y corresponding to the given x

    ' rX and rY must be equal-length vectors
    ' rX must be sorted ascending or decreasing

    Dim i       As Long     ' index to rY
    Dim dF      As Double   ' interpolation fraction
    Dim v       As Variant  ' for each/loop control variable

    For Each v In Array(rX, rY)
        If v.Areas.Count > 1 Then GoTo Oops
        If v.Rows.Count <> 1 And v.Columns.Count <> 1 Then GoTo Oops
        If WorksheetFunction.Count(v) <> v.Count Then GoTo Oops
    Next v
    If rX.Count < 2 Then GoTo Oops
    If rX.Count <> rY.Count Then GoTo Oops

    dFrac x, rX, i, dF, IIf(rX(rX.Count).Value2 > rX(1).Value2, 1, -1)
    LINTERP = rY(i).Value2 * (1 - dF) + rY(i + 1).Value2 * dF
    Exit Function

Oops:
    LINTERP = CVErr(xlErrValue)
End Function

In C2 and copy down,

=LINTERP(A3,$D$3:$D$337,$E$3:$E$337)

... then plot columns B & C