问题
I use vba on excel 2007, OS: windows vista, to make calculation using kinematic wave equation in finite difference scheme. But, when it runs the run-time 5 (invalid procedure call or arguments) message appears. I really don't what is going wrong. Anyone can help?
Sub kwave()
Dim u(500, 500), yy(500, 500), alpha, dt, dx, m, n, so, r, f, X, L, K As Single
Dim i, j As Integer
dx = 0.1
dt = 0.01
L = 10
m = 5 / 3
r = 1
f = 0.5
n = 0.025
so = 0.1 'this is slope
alpha = 1 / n * so ^ 0.5
X = 0
For i = 0 To 100
Cells(i + 1, 1) = X
u(i, 1) = L - so * X
X = X + dx
Cells(i + 1, 2) = u(i, 1)
Next i
For j = 0 To 100
For i = 1 To 100
'predictor step
u(i, j + 1) = u(i, j) - alpha * dt / dx * (u(i + 1, j) ^ m - u(i, j) ^ m) + (r - f) * dt
'corrector step
K = u(i, j + 1) ^ m - u(i - 1, j + 1) ^ m '<<<<----- RUNTIME ERROR 5 HAPPENS AT THIS LINE
yy(i, j + 1) = 0.5 * ((yy(i, j) + u(i, j + 1)) - alpha * dt / dx * K + (r - f) * dt)
Next i
Next j
End Sub
回答1:
You are declaring the variables wrong- the array should store a double/single but it is defaulting to a variant. See this article.
http://www.cpearson.com/excel/declaringvariables.aspx -
"Pay Attention To Variables Declared With One Dim Statement
VBA allows declaring more than one variable with a single Dim statement. I don't like this for stylistic reasons, but others do prefer it. However, it is important to remember how variables will be typed. Consider the following code:
Dim J, K, L As Long You may think that all three variables are declared as Long types. This is not the case. Only L is typed as a Long. The variables J and K are typed as Variant. This declaration is functionally equivalent to the following:
Dim J As Variant, K As Variant, L As Long You should use the As Type modifier for each variable declared with the Dim statement:
Dim J As Long, K As Long, L As Long "
Additionally, when i = 99 and j = 10, u(99,11), which is j+1, produces a negative number. Note that this does not fully cause the problem though, because you can raise negative numbers to exponents. Ex, -5^3 = -125
来源：https://stackoverflow.com/questions/28390833/run-time-error-5-in-vba-excel-when-working-with-array