April 22nd, 2007, 03:57 PM

Function which returns true with a given probability
I need to create a function which returns true with a given probability. For example:
foo(.1) returns true with probability .1
Could someone provide either a ruby implementation or a generic way to do this?
April 24th, 2007, 08:23 AM

Code:
public boolean foo(double probability) {
return true;
}
Seriously, You've got to specify some more logical requirements than that.
Dear God. What is it like in your funny little brains? It must be so boring.
April 26th, 2007, 02:47 AM

I've said plenty. The technical term for what I have described is weighted random selection. In this case, the selection is between two elements: true and false. The probability p, given as an argument, is the weight assigned to true, and therefore the weight assigned to false is 1p.
I ended up finding a Ruby implementation of weighted random selection that works for any number of elements; using this, I wrote my function.
April 26th, 2007, 11:13 AM

Its one of those things you have to read twice. Trust me, he isn't usually so "outofit". Also, welcome to Dev Shed =D
"Java makes impossible things possible, but makes easy things difficult."  Somebody
April 26th, 2007, 04:18 PM

Its one of those things you have to read twice.
Agreed. Also, I probably could have done better job explaining what I was looking for.
April 26th, 2007, 05:58 PM

Use a PRNG.
Say you take a probability out of 100. So for foo(.1), that's really like saying, I have a random number from 1100. Is it less than 10? A standard PRNG available in most languages gives you a uniform distribution, so the probability is .1 that the number is less than 10. So look up creating random numbers in Ruby.
Generate random number within a range (something like 1100, 11000). Check if random number is less than probability*range. If it is, return true, otherwise return false.
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