I have created a function via vba and I have used this function to make an iterative table. I have set the workbook calculation to automatic and it all works fine but when I open the excel file, the cells that contain the mentioned function, give me #name error and everytime I need to recalculate. Is there a way to fix this?
Public Function FrictionFactor(relativeroughness, reynoldsnumber)
'Dim relativeroughness, reynoldsnumber As Double
fNext = 0.005 ' initial value for f
fIncrement = 0.005 ' initial step size
Convergence = 0.000001 ' sets the decimal place accuracy of the result
Do
fStart = fNext
LHSColebrookStart = 1 / (fStart ^ 0.5)
RHSColebrookStart = -2 * (Log((relativeroughness / 3.7) + (2.51 / (reynoldsnumber * (fStart ^ 0.5)))) / Log(10))
DifferenceStart = LHSColebrookStart - RHSColebrookStart
fNext = fStart + fIncrement
LHSColebrookNext = 1 / (fNext ^ 0.5)
RHSColebrookNext = -2 * (Log((relativeroughness / 3.7) + (2.51 / (reynoldsnumber * (fNext ^ 0.5)))) / Log(10))
DifferenceNext = LHSColebrookNext - RHSColebrookNext
If DifferenceStart * DifferenceNext < 0 Then ' march f in opposite direction and more slowly
fIncrement = fIncrement / -10
ElseIf DifferenceStart * DifferenceNext = 0 Then ' done
fIncrement = 0
End If ' keep marching f in same direction and at same rate
Loop While Abs(fStart - fNext) > Convergence
FrictionFactor = fStart
End Function
The usual reason this happens is that macros are not enabled when the workbook is opened. Check your Security settings.
Related
I just wrote this code to perform an iterative calculation. It finds the X,Y coordinates where an unknown parabola is tangent to a known circle. It is based on other iterative functions I've written that have worked flawlessly. I'm stumped as to what the issue is. Here is the code:
Public Function Jext(PA As Double, Xcl As Double, Ycl As Double, Ctr As Double, Rnl As Double, Finl As Double) As Double
Pi = 3.14159265358979
tol = 0.00000001
Dim x(20) As Double
Dim Yc(20) As Double
Dim Yp(20) As Double
Dim A(20) As Double
Dim Diff(20) As Double
Dim It As Integer
Dim hF As Double
Dim Sf As Double
'Xcl is the horizontal position of the root radius center line
'Ycl is the vertical position of the root radius center line
'Ctr is root radius. It's an approximation of the trochoid and is typically the cutter tip radius
'Rnl is the radius to the point where the load line intersects the tooth centerline. It is the apex of the parabola
'x is the horizontal position that is common to the parabola and circle. It is the independent variable
'Yc is the vertical position on the circle at point x
'Yp is the vertical position on the parabola at point x
'A is the leading term of the parabolic equation
'Diff is the calculated difference in vertical positions of circle and parabola
'Set initial guess values. x(0) is 5% of the radius (left edge of circle) and x(1) is 95% of the radius(bottom of the circle)
x(0) = (Xcl - Ctr) + 0.05 * Ctr
x(1) = (Xcl - Ctr) + 0.95 * Ctr
Yc(0) = Ycl - (Ctr ^ 2 - (x(0) - Xcl) ^ 2) ^ 0.5
Yc(1) = Ycl - (Ctr ^ 2 - (x(1) - Xcl) ^ 2) ^ 0.5
A(0) = Tan(WorksheetFunction.Acos((Xcl - x(0)) / Ctr) + Pi / 2) / (2 * x(0))
A(1) = Tan(WorksheetFunction.Acos((Xcl - x(1)) / Ctr) + Pi / 2) / (2 * x(1))
Yp(0) = A(0) * x(0) ^ 2 + Rnl
Yp(1) = A(1) * x(1) ^ 2 + Rnl
Diff(0) = Yp(0) - Yc(0)
Diff(1) = Yp(1) - Yc(1)
For It = 1 To 19 Step 1
x(It + 1) = x(It) - (Diff(It) - 0) * (x(It - 1) - x(It)) / (Diff(It - 1) - Diff(It))
Yc(It + 1) = Ycl - (Ctr ^ 2 - (x(It + 1) - Xcl) ^ 2) ^ 0.5
A(It + 1) = Tan(WorksheetFunction.Acos((Xcl - x(It + 1)) / Ctr) + Pi / 2) / (2 * x(It + 1))
Yp(It + 1) = A(It + 1) * x(It + 1) ^ 2 + Rnl
Diff(It + 1) = Yp(It + 1) - Yc(It + 1)
If Abs(Diff(It + 1)) < tol Then Exit For
Debug.Print Diff(It + 1)
Next It
hF = Rnl - Yp(t + 1)
Sf = 2 * x(t + 1)
Jext = 1 / (Cos(Finl) / Cos(PA) * (6 * hF / Sf ^ 2 - Tan(Finl) / Sf))
End Function
I put a stop at the "Next It" line to check the values as it went through the iterative loops. When I execute the code, all of the values are as expected and the value of Abs(Diff(It+1)) is not small enough to exit the for loop in the IF statement. I put the Debug.Print statement in there to make sure it was getting that far in the code and it did print Diff(It+1). So it executes everything to that point. Then when I continue the function it just stops and returns a #VALUE error in the spreadsheet. I've no idea why it won't continue the for loop. Anyone see something I've missed?
I'm trying to make a label move from one cell to another. I figured out the position offsets and created 3 "tweens" as animators call them. But when I run the code, the Label doesn't display until the sub has ended. If I comment out the last position the label is in the right spot. How do I make Excel update the screen to show the label before I move it again?
xo and yo are integers either -1, 0, or 1. playerLocation is a range, might as well be ActiveCell.
Sub moveAnimation()
Dim moveAnim As OLEObject
Set moveAnim = Worksheets(currentSheet).OLEObjects(currentSheet & "player")
moveAnim.Left = playerLocation.Left - 0.5 + yo * (playerLocation.Width / 4)
moveAnim.Top = playerLocation.Top + 0.25 + xo * (playerLocation.Width / 4)
Sleep (25)
moveAnim.Left = playerLocation.Left - 0.5 + yo * (playerLocation.Width / 2)
moveAnim.Top = playerLocation.Top + 0.25 + xo * (playerLocation.Width / 2)
Sleep (25)
moveAnim.Left = playerLocation.Left - 0.5 + yo * 3 * (playerLocation.Width / 4)
moveAnim.Top = playerLocation.Top + 0.25 + xo * 3 * (playerLocation.Width / 4)
Sleep (25)
moveAnim.Left = 0
moveAnim.Top = 0
I've figured it out. ActiveSheet.Calculate will force an update so i put it between each position
I am looking at VBA code (function) written by someone else.
Here is the code:
Function EuropeanDelta(StrikePrice, MarketPrice, Volatility, InterestRate As Double, PC As String, ValueDate, ExpiryDate As Date, Optional PriceOrYield As String = "P") As Double
Rem Declare our working variables
Dim r As Double
Dim d1 As Double
Dim d2 As Double
Dim t As Double
Dim SqT As Double
Rem End of variable declaration
If PriceOrYield = "Y" Then
MarketPrice = 100 - MarketPrice
StrikePrice = 100 - StrikePrice
If PC = "C" Then
PC = "P"
Else
PC = "C"
End If
End If
Rem Initiase our working variables
t = (ExpiryDate - ValueDate) / 365
SqT = Sqr(t)
r = Application.WorksheetFunction.Ln(1 + InterestRate)
d1 = (Application.WorksheetFunction.Ln(MarketPrice / StrikePrice) + (Volatility * Volatility * 0.5) * t) / (Volatility * SqT)
Rem Quick logic to deal with Calls or Puts
If PC = "C" Then
EuropeanDelta = Exp(-r * t) * Application.WorksheetFunction.NormSDist(d1)
Else
EuropeanDelta = -Exp(-r * t) * Application.WorksheetFunction.NormSDist(-d1)
End If
If PriceOrYield = "Y" Then
EuropeanDelta = EuropeanDelta * -1
End If
End Function
The whole problem is based around the line for "d1". I would like to re-organise to solve for "StrikePrice". I have tried writing it out mathematically and then re-arranging, then swapping back to VBA.
#duffymo is correct, but am giving the answer directly in terms of VBA code
' d1 = (Log(MarketPrice / StrikePrice) + (Volatility * Volatility * 0.5) * t) / (Volatility * Sqr(t))
'
' Volatility * Sqr(t) * d1 = Log(MarketPrice / StrikePrice) + Volatility^2 * t/2
'
' Log(MarketPrice / StrikePrice) = Volatility * Sqr(t) * d1 - Volatility^2 * t/2
'
' MarketPrice / StrikePrice = Exp(Volatility * Sqr(t) * d1 - Volatility^2 * t/2)
'
StrikePrice = MarketPrice / Exp(Volatility * Sqr(t) * d1 - Volatility^2 * t/2)
Other Notes :
For brevity replace Application.WorksheetFunction.Ln() with Log()
There is no need cache SqT = Sqr(t) since it is only used once.
For clarity replace Volatility*Volatility with Volatility^2 as internally it does the same thing.
This is just algebra - high school math.
Take it in steps. Make sure you do the same operation to both sides to make sure that equality still holds.
Here's your starting equation:
d = {ln(m/s) + v*v*t/2}/(v*sqrt(t))
Multiply both sides by the denominator of the RHS:
d*v*sqrt(t) = ln(m/s) + v*v*t/2
Subtract v*v*t/2 from both sides:
(d*v*sqrt(t) - v*v*t/2) = ln(m/s)
Apply the exponential function to both sides, noting that exp(ln(x)) = x:
exp(d*v*sqrt(t) - v*v*t/2) = m/s
Multiply both sides by s:
s*exp(d*v*sqrt(t) - v*v*t/2) = m
Divide both sides by exp(d*v*sqrt(t) - v*v*t/2) to get the desired result:
s = m/exp(d*v*sqrt(t) - v*v*t/2)
Let's see if this function makes sense.
At t = 0 the denominator exp(0) = 1, so the strike price is equal to the market price.
As t -> infinity, we hope that the denominator gets large so s -> zero. L'Hospital's Rule will help here.
I am trying to achieve the Ramanujan Function by using VBA. The formula is in the picture below.
My code is:
Function ramanuian(n)
left_part = (Application.sqrt(8) / 9801)
Dim temp As Double
temp = 0
For i = 0 To n
middle_part = Application.Fact(4 * i) / Application.Power(Application.Fact(i), 4)
right_part = (1103 + 26930 * i) / Application.Power(396, 4 * i)
ramanuian_reciprocal = middle_part * right_part
temp = temp + ramanuian_reciprocal
Next
ramanuian = 1 / (left_part * temp)
End Function
However, when I run this formula in Excel, it shows me an #Value! error. What is wrong with my code?
I've got a set of equations which I'd like to be repeated taking variables from the next row down for each of the columns at which each variable is located. I am a beginner, so my coding is probably not to scratch:
Sub Iteration()
Dim al, ab, ae As Double
Dim as1, as2 As Double
'etc
as1 = Range("CG7")
as2 = Range("CG8")
aA1 = Range("BQ7")
'etc
intCounter = 0
For intCounter = 1 To 10000
Let x = ((aN1 * 1000) - (as1 * aA1) + (as2 * aA2)) / (al * fc * ae * ab)
Let x2 = ((aN12 * 1000) - (as12 * aA12) + (as22 * aA22)) / (al2 * fc2 * ae2 * ab2)
Next
Sheets("Sheet1").Range("CJ7").Value = x
End Sub
I've done this for several variables which I've set as the range relative to each variable value. And then for the next row I've had to redo the whole equation and set the variables again for the next row down. Is there any way to set the variables (possibly with a relative cell reference?) which will skip to the cell in the next row for the next calculation? Consider also that there are 36 rows for calculation and about 9 variables!
If I understand you correctly, how about something like this:
Sub Iteration()
Dim al, ab, ae As Double
Dim as1, as2 As Double
'etc
intCounter = 0
For intCounter = 0 To 10000
as1 = Range("CG7").Offset(intCounter)
as2 = Range("CG8").Offset(intCounter)
aA1 = Range("BQ7").Offset(intCounter)
'etc
Let x = ((aN1 * 1000) - (as1 * aA1) + (as2 * aA2)) / (al * fc * ae * ab)
Let x2 = ((aN12 * 1000) - (as12 * aA12) + (as22 * aA22)) / (al2 * fc2 * ae2 * ab2)
Next
Sheets("Sheet1").Range("CJ7").Value = x
End Sub