Hi, Timothy,
Here are a couple of functions that I think will fit the bill for
you. The first returns a number in standard normal distribution
(mean 0 and standard deviation 1). The second returns a number in
normal distribution with mean mu and standard deviation sigma (as
arguments.
They are followed by handlers to print out a histogram for 10000 numbers
function stdNormDist
constant fourG = 4000000000
return sqrt(-2*ln(1-random(fourG)/ fourG))*cos(random(fourG)/
fourG *2*pi)
end stdNormDist
function normDist mu, sigma
return sigma * stdNormDist() + mu
end normDist
on tst
put 10 into sigma
put 100 into mu
repeat with i = 0 to 32
put 0 into hist[i]
end repeat
repeat with i = 1 to 10000
put normDist(mu, sigma) into nD
put (nD - mu) / sigma into nSDs
put max(0,min(32,round(nSDs*4)+16)) into ndx -- 4 slots per
std dev
add 1 to hist[ndx]
end repeat
put printHistLine(hist[0]) into printTmp
repeat with i =1 to 32
put return & printHistLine(hist[i]) after printTmp
end repeat
put printTmp
end tst
function printHistLine histCount
put round(histCount/25) into hCount
return "|" & multiStr("x", hCount) && histCount
end printHistLine
function multiStr str, n
put empty into tmp
repeat n times
put str after tmp
end repeat
return tmp
end multiStr
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From: Timothy Miller <[EMAIL PROTECTED]>
Subject: Gaussian pseudo-random numbers -- math issues
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