Non-uniform random distribution: How do I get a random between 100 and 180 that is on average close to 120? (like in a Gaussian distribution)

Presume I have the following case:

• int value a

• int value b, for which a






• int value i, for which a

• I need an int value x, for which a




In Java, I have the following methods available on java.util.Random:



• nextInt(int m): int between 0 and m






• nextDouble(): double between 0.0 and 1.0






• nextGaussian(): double between -Infinity and +Infinity, usually close to 0.0.




How do I build such a non-uniform distribution from these building blocks? How do I reliably and efficiently transform nextGaussian() into nextGaussian(a, b, i)`? The part I am struggling with is to enforce that x is selected between a and b (without doing a trial-and-error).

Your problem is rather vague: "bell curve" and "centered around i" are not well defined.

One possible recipe is to generate a truncated gaussian: define s= min(b-i,i-a)/c where c is a free parameter (suggested values: [1,3] range), generate a gaussian with mean i and standard deviation s - and round it to the nearest integer. If the value falls outside the [a,b] range, try again.

Related.

StackExchange Computer Science Q#18467, answer score: 5