mathjs/lib/esm/function/arithmetic/log.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif

import { factory } from '../../utils/factory.js';
import { promoteLogarithm } from '../../utils/bigint.js';
import { logNumber } from '../../plain/number/index.js';
var name = 'log';
var dependencies = ['config', 'typed', 'typeOf', 'divideScalar', 'Complex'];
var nlg16 = Math.log(16);
export var createLog = /* #__PURE__ */factory(name, dependencies, _ref => {
  var {
    typed,
    typeOf,
    config,
    divideScalar,
    Complex
  } = _ref;
  /**
   * Calculate the logarithm of a value.
   *
   * To avoid confusion with the matrix logarithm, this function does not
   * apply to matrices.
   *
   * Syntax:
   *
   *    math.log(x)
   *    math.log(x, base)
   *
   * Examples:
   *
   *    math.log(3.5)                  // returns 1.252762968495368
   *    math.exp(math.log(2.4))        // returns 2.4
   *
   *    math.pow(10, 4)                // returns 10000
   *    math.log(10000, 10)            // returns 4
   *    math.log(10000) / math.log(10) // returns 4
   *
   *    math.log(1024, 2)              // returns 10
   *    math.pow(2, 10)                // returns 1024
   *
   * See also:
   *
   *    exp, log2, log10, log1p
   *
   * History:
   *
   *    v0.0.2  Created
   *    v0.2    Add optional base argument
   *    v0.3    Handle Array input
   *    v0.5    Handle Matrix input
   *    v0.16   Handle BigNumber input
   *    v0.21   Support negative BigNumbers
   *    v11     Drop Array/Matrix support in favor of explicit map of
   *            the scalar log function, to avoid confusion with the log
   *            of a matrix
   *    v14     Allow value and base to be Fractions, when the log is rational
   *
   * @param {number | BigNumber | Fraction | Complex} x
   *            Value for which to calculate the logarithm.
   * @param {number | BigNumber | Fraction | Complex} [base=e]
   *            Optional base for the logarithm. If not provided, the natural
   *            logarithm of `x` is calculated.
   * @return {number | BigNumber | Fraction | Complex}
   *            Returns the logarithm of `x`
   */
  function complexLog(c) {
    return c.log();
  }
  function complexLogNumber(x) {
    return complexLog(new Complex(x, 0));
  }
  return typed(name, {
    number: function number(x) {
      if (x >= 0 || config.predictable) {
        return logNumber(x);
      } else {
        // negative value -> complex value computation
        return complexLogNumber(x);
      }
    },
    bigint: promoteLogarithm(nlg16, logNumber, config, complexLogNumber),
    Complex: complexLog,
    BigNumber: function BigNumber(x) {
      if (!x.isNegative() || config.predictable) {
        return x.ln();
      } else {
        // downgrade to number, return Complex valued result
        return complexLogNumber(x.toNumber());
      }
    },
    'any, any': typed.referToSelf(self => (x, base) => {
      // calculate logarithm for a specified base, log(x, base)

      if (typeOf(x) === 'Fraction' && typeOf(base) === 'Fraction') {
        var result = x.log(base);
        if (result !== null) {
          return result;
        }
      }
      return divideScalar(self(x), self(base));
    })
  });
});