Good idea, some commonly used math functions ....
Code:
Function fact(arg1 as double) as double
''Returns the factorial (n!)
Dim ct as integer
Dim tempval as double
arg1=int(arg1)
if arg1=0 or arg1=1 then
fact=1
exit function
end if
ct=1
tempval=1
do
ct=ct+1
if arg1>=ct then
tempval=tempval*ct
else
exit do
end if
loop
fact=tempval
End Function
Function snorm(z As Double) as double
''Returns the cummulative normal distribution
Dim pi as double
pi=3.14159265358979
Dim a1 as double,a2 as double,a3 as double,a4 as double,a5 as double,k as double,w as double
a1 = 0.31938153
a2 = -0.356563782
a3 = 1.781477937
a4 = -1.821255978
a5 = 1.330274429
If 0 > z Then w = -1 Else w = 1
k = 1 / (1 + 0.2316419 * w * z)
snorm = 0.5 + w * (0.5 - 1 / Sqr(2 * pi) * Exp(-z ^ 2 / 2) * (a1 * k + a2 * k ^ 2 + a3 * k ^ 3 + a4 * k ^ 4 + a5 * k ^ 5))
End Function
FUNCTION snormInv(p AS DOUBLE) as double
''Returns the z value for a given probability
Dim Minz as double,Maxz as double,zVal as double,pVal as double,prec as double
prec = 1e-06
Minz = -6.0
Maxz = 6.0
zVal = 0.0
WHILE (Maxz - Minz) > prec
pVal = snorm(zVal)
IF pVal > p THEN
Maxz = zVal
ELSE
Minz = zVal
END IF
zVal = (Maxz + Minz) * 0.5
WEND
snorminv = zVal
END FUNCTION
Function Combin(arg1 as double,arg2 as double) as double
''Returns the available Combinations
''arg1 -> number n
''arg2 -> number k
Dim tempvalue1 as double, tempvalue2 as double
Dim ct as integer
if int(arg1)<0 or int(arg2)<0 or int(arg1)<int(arg2) then
Combin=0
''TheError=1
Exit Function
end if
if int(arg2)=0 then
Combin=1
Exit Function
end if
tempvalue2=1
tempvalue1=1
for ct=1 to int(arg2)
tempvalue2=tempvalue2*ct
next ct
for ct=(int(arg1)-int(arg2)+1) to int(arg1)
tempvalue1=tempvalue1*ct
next ct
Combin=tempvalue1/tempvalue2
End Function
Function Permut(arg1 as double,arg2 as double) as double
''Returns the available Permutations
'arg1 -> number n
'arg2 -> number k
Dim tempvalue1 as double
Dim ct as integer
if int(arg1)<0 or int(arg2)<0 or int(arg1)<int(arg2) then
Permut=0
''TheError=1
Exit Function
end if
if int(arg2)=0 then
Permut=1
Exit Function
end if
tempvalue1=1
for ct=(int(arg1)-int(arg2)+1) to int(arg1)
tempvalue1=tempvalue1*ct
next ct
Permut=tempvalue1
End Function
Function BinomDist(arg1 as double,arg2 as double,arg3 as double,arg4 as integer) as double
''Returns the Binomial probability
''arg1 -> number S
''arg2 -> number of trials
''arg3 -> prob of S
''arg4 -> Cumulative
Dim i as double
Dim s as double
if int(arg2)<0 or int(arg1)<0 or int(arg2)<int(arg1) or arg3>1 or arg3<0 then
BinomDist=0
''TheError=1
exit function
end if
Select Case arg4
Case 0
BinomDist = Combin(arg2,arg1)*arg3^(int(arg1))*(1-arg3)^(int(arg2)-int(arg1))
Case 1
s=0
for i=0 to arg1
s=s+Combin(arg2,i)*arg3^i*(1-arg3)^(int(arg2)-i)
next i
BinomDist=s
Case else
''TheError=1
BinomDist=0
End Select
End Function
Function Poisson(arg1 as double,arg2 as double,arg3 as integer) as double
''Returns the Poisson probability
''arg1 -> number S
''arg2 -> mean
''arg3 -> Cumulative
Dim i as double
Dim s as double
if int(arg1)<0 or arg2<0 then
Poisson=0
''TheError=1
Exit Function
end if
Select Case arg3
Case 0
Poisson = exp(-arg2)*arg2^arg1/fact(arg1)
Case 1
s=0
for i=0 to arg1
s=s+exp(-arg2)*arg2^i/fact(i)
next i
Poisson=s
Case else
''TheError=1
Poisson=0
End Select
End Function
'' tests
Print "fact(5)= ";fact(5)
Print "snorm(2)= ";snorm(2)
Print "snorminv(0.5)= ";snorminv(0.5)
Print "combin(5,3)= ";combin(5,3)
Print "permut(5,3)= ";permut(5,3)
Print "BinomDist(3,5,0.5,0)= ";BinomDist(3,5,0.5,0)
Print "Poisson(3,5,0)= ";Poisson(3,5,0)
sleep
