simple-statistics/src/bernoulli_distribution.js

Simple Statistics

/**
 * The [Bernoulli distribution](http://en.wikipedia.org/wiki/Bernoulli_distribution)
 * is the probability discrete
 * distribution of a random variable which takes value 1 with success
 * probability `p` and value 0 with failure
 * probability `q` = 1 - `p`. It can be used, for example, to represent the
 * toss of a coin, where "1" is defined to mean "heads" and "0" is defined
 * to mean "tails" (or vice versa). It is
 * a special case of a Binomial Distribution
 * where `n` = 1.
 *
 * @param {number} p input value, between 0 and 1 inclusive
 * @returns {number[]} values of bernoulli distribution at this point
 * @throws {Error} if p is outside 0 and 1
 * @example
 * bernoulliDistribution(0.3); // => [0.7, 0.3]
 */
function bernoulliDistribution(p) /*: number[] */ {
    // Check that `p` is a valid probability (0 ≤ p ≤ 1)
    if (p < 0 || p > 1) {
        throw new Error(
            "bernoulliDistribution requires probability to be between 0 and 1 inclusive"
        );
    }

    return [1 - p, p];
}

export default bernoulliDistribution;