var Prob = require('prob.js');

var r = Prob.normal(0, 1.0); // μ = 0, σ = 1.0 
r(); // Returns a random number from this distribution
r(); // Returns another random number
r(); // and again

Prob.uniform(min, max) // Uniform distribution in range [min, max).
Prob.normal(μ, σ)      // Normal distribution with mean and standard deviation.
Prob.exponential(λ)    // Exponential distribution with lambda.
Prob.lognormal(μ, σ)   // Log-normal distribution defined as ln(normal(μ, σ)).
Prob.poisson(λ)        // Poisson distribution returning integers >= 0.
Prob.zipf(s, N)        // Zipf's distribution returning integers in range [1, N].

var r = Prob.exponential(1.0); // Create a distribution.
r()        // Generates a number within the distribution.
r(src)     // Generates a number using a `src` of random numbers. (See note below.)
r.Min      // The min random number which could be returned by `r()` (inclusive).
r.Max      // The max random number which could be returned by `r()` (exclusive).
r.Mean     // The expected mean for this distribution.
r.Variance // The expected variance for this distribution.

// https://xkcd.com/221/
function xkcd_source() {
	return 4; // chosen by fair dice roll.
	          // guaranteed to be random.
};

var r = Prob.exponential(1.0); // Create a distribution.

// Use the XKCD source
console.log( r(xkcd_source) );

// Or use a better source (supplied by random-js)
console.log( r(Random.engines.browserCrypto) );

// Or just use the default which happens to be Random.engines.mt19937().autoSeed()
console.log( r() );