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I'm writing a paper on an application I wrote, and I'm trying to describe mathematically what I did to determine the rotation of an object. What I did is really simple, but my math lags far behind my computer science.

What it does is select a random number between min and max. 0 <= min, max < 1 If min > max, in which case it selects a random number between min and max and subtracts 1 if the number is greater than 1. (i.e. the number under (mod 1))

This is what I'm saying right now:

When determining an orientation, the orientation is selected from the valid orientations, then a random number x is selected such that

enter image description here

Where min is the minimum offset, max is the maximum offset, and 0≤min,max<1. The radian measure of the orientation would be 2πx, and the degree measure would be 360x°.

This is the code in question:

if (min > max)
{
    double d = Utility.r.NextDouble() * (max + 1 - min) + min;
    if (d >= 1)
        d -= 1;
    return d;
}
else
{
    double d = Utility.r.NextDouble() * (max - min) + min;
    return d;
}
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If you are just trying to say that the function generates a random number in the interval $[0,1)$, then that is all you really need to say. However, if you really do need to describe the exact way you're implementing this then you might want to try optimizing/refactoring your code to attain a more elegant solution. The math would then follow more readily. –  pbs Aug 14 '12 at 16:48
    
@pbs Just thinking about math forced me to realize this could easily be done in a single line. I still have a very similar issue with expressing selecting a random number from a set, so I'll just follow Greg Martin's advice. –  Ryan Amos Aug 14 '12 at 17:29
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1 Answer 1

up vote 3 down vote accepted

I think this is much easier to state in words than in mathematical notation. "We are given two real numbers min and max between 0 and 1. The function we coded selects a random real number between 0 and 1 as follows: if min < max, then we select a real number uniformly from the interval [min, max); if min > max, we select a real number uniformly from the interval [max, min+1), and then reduce the resulting number modulo 1."

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