Get a random number focused on center

javascript algorithm random numbers
Darryl Huffman picture Darryl Huffman · May 27, 2015 · Viewed 15.6k times · Source

Is it possible to get a random number between 1-100 and keep the results mainly within the 40-60 range? I mean, it will go out of that range rarely, but I want it to be mainly within that range... Is it possible with JavaScript/jQuery?

Right now I'm just using the basic Math.random() * 100 + 1.

Answer

BlueRaja - Danny Pflughoeft picture BlueRaja - Danny Pflughoeft · May 28, 2015

The simplest way would be to generate two random numbers from 0-50 and add them together.

This gives a distribution biased towards 50, in the same way rolling two dice biases towards 7.

In fact, by using a larger number of "dice" (as @Falco suggests), you can make a closer approximation to a bell-curve:

function weightedRandom(max, numDice) {
    let num = 0;
    for (let i = 0; i < numDice; i++) {
        num += Math.random() * (max/numDice);
    }    
    return num;
}

Weighted random numbers

JSFiddle: http://jsfiddle.net/797qhcza/1/

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