Excel VBA #Value! Error - vba

Question

I have the following function that when I run it says #value! error.
I would appreciate any help.
Function Bootstrap(S As Object, Z As Object, L As Double)
Dim j As Integer
Dim a() As Double
Dim b() As Double
Dim n As Integer
Dim Q() As Double
Dim sum As Double
Dim P As Double
ReDim a(1 To n)
ReDim b(1 To n)
ReDim Q(1 To n)
dt = 1
sum = 0
Q(0) = 0
For j = 1 To n - 1
S.Cells(j, 1).Value = a(j)
Z.Cells(j, 2).Value = b(j)
P = Z(j) * (L * Q(j-1) - (L + dt * a(n) * Q(j))
sum = sum + P
Next j
Bootstrap = sum
End Function
Bootstrapping function calculates the following value
In fact I am trying to calculate this formula
Q(t,Tn)=(∑(j=1)to(n-1) Z(t,Tj)[LQ(t,Tj-1)-(L+dtSn)Q(t,Tj)]/[Z(t,Tn)(L+dt*Sn)] +(Q(t,Tn-1)L)/(L+dtSn)
Inputs given are[S1 ,S2,….Sn ],[Z(t,T1),Z(t,T2)…..Z(t,Tn)]and and L=0.4

Answer 1

Try this code : entered as =Bootstrap(A1:B1,A2:B2,0.4)
I have corrected the following
- Assigning the ranges to variants
- defining dt as double
- Dim Q() as 0 to n
- using A() and b() in the formula
- the input ranges are rows not columns
Function Bootstrap(S As Range, Z As Range, L As Double) As Double
Dim j As Integer
Dim a As Variant
Dim b As Variant
Dim n As Integer
Dim Q() As Double
Dim sum As Double
Dim P As Double
Dim dt As Double
n = Application.WorksheetFunction.Max(S.Columns.Count, Z.Columns.Count)
a = S.Value
b = Z.Value
dt = 1
sum = 0
ReDim Q(0 To n)
Q(0) = 0
For j = 1 To n - 1
P = b(1, j) * (L * Q(j - 1)) - (L + dt * a(1, j) * Q(j - 1))
sum = sum + P
Q(j) = sum
Next j
Bootstrap = sum
End Function

Answer 2

Take the habit to format and increment your code, especially before posting it!
You need to type the output of the function (on the line of the function name)
A parenthesis is missing from the line P = Z(j) * (L*Q(j-1)-(L+ dt * a(n) * Q(j))
n is empty (and so are a, b and Q) when you try to redim your arrays, so you need to define them!
Z(j) will also give you an error, because it is a Range, you need Z.Cells(i,j)
Try this :
Function Bootstrap(S As Range, Z As Range, L As Double) As Double
Dim j As Integer
Dim a() As Double
Dim b() As Double
Dim n As Integer
Dim Q() As Double
Dim sum As Double
Dim P As Double
n = Application.WorksheetFunction.Max(S.Columns.count, Z.Columns.count)
a = S.Value
b = Z.Value
dt = 1
sum = 0
ReDim Q(1 To n)
Q(0) = 0
'Q(1) = "??"
For j = 1 To n - 1
P = b(1, j) * (L * Q(j - 1)) - (L + dt * a(1, j) * Q(j - 1))
sum = sum + P
Q(j) = sum
Next j
Bootstrap = sum
End Function