Triangular Distribution using VBA

Hi pogo and welcome to the forum,

I get an error in compiling the function as "prob(1)" is not defined. What is prob(1) supposed to be??

cumProb = Prob(1):
1. Prob does not correspond to syntax and description of the Worksheetfunction per Microsoft.:

PROB(x_range,prob_range,lower_limit,upper_limit)

2. CumProb is never used in the function.

Option Explicit
Function Triangular(a As Single, b As Single, c As Single) As Double
    Randomize
    Application.Volatile
    
    Dim d As Single
    Dim cumProb As Single
    Dim uniform As Single
    Dim RetVal  As Single
    
    d = (b - a) / (c - a)
    uniform = Rnd()
    'cumProb = Prob(1)

    If uniform < d Then
        Triangular = a + (c - a) * Sqr(d * uniform)
    Else
        Triangular = a + (c - a) * (1 - Sqr(1 - d) * (1 - uniform))
    End If

End Function

Sub caller()
    Debug.Print Triangular(3, 4, 6)   ======> returns  5.47996471111746 
End Sub

No, in a cell it should be cell addresses. for example:
=Triangular(A1,A2,A3)

That would be one potential function call. You could also put any/all of those values into cells and use cell references =Triangular(A1,B1,C1) where A1 is 3, B1 is 4, and C1 is 6.

I note that you are using Singles for the arguments and calculations. I have seen at least one case on this forum where the poster had some concerns with the way that Excel/VBA converted a result from Single to Double, since that conversion will not always be exact. I guess I just wonder if there is a reason you are using the Single data type rather than the Double data type for all variables.

@marium.k: This forum usually doesn't like it when you post your question in the thread of another member. They would prefer that you start your own thread. If this thread will help others understand your question, include a link to this thread in your post. When you start your own thread, it will probably be important to know exactly what code you are using, how you are using it, and what error you are getting.