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isUnityProbabilityArray
Test if a value is an array of probabilities that sum to one.
Installation
npm install @stdlib/assert-is-unity-probability-array
Usage
var isUnityProbabilityArray = require( '@stdlib/assert-is-unity-probability-array' );
isUnityProbabilityArray( value )
Tests if a value
is an array of probabilities that sum to one.
var Uint8Array = require( '@stdlib/array-uint8' );
var bool = isUnityProbabilityArray( [ 0.25, 0.5, 0.25 ] );
// returns true
bool = isUnityProbabilityArray( new Uint8Array( [ 0, 1 ] ) );
// returns true
bool = isUnityProbabilityArray( [ 3.14, 0.0 ] );
// returns false
Notes
-
Summation of finite-precision floating-point numbers often has numerical error. For example,
var arr = [ 0.1, 0.2, 0.1, 0.1, 0.2, 0.2, 0.1 ]; // => 1.0 var sum = 0.0; var i; for ( i = 0; i < arr.length; i++ ) { sum += arr[ i ]; } console.log( sum ); // => 0.9999999999999999
To account for numerical error, the function tests if array elements sum to approximately one; specifically,
1.0 - sqrt(eps) <= sum(A) <= 1.0 + sqrt(eps)
where
eps
is double-precision floating-point epsilon (~2.22e-16
) andsqrt(eps) ~ 1.49e-8
. The above comparison ensures equality for approximately half the significand bits.
Examples
var Uint8Array = require( '@stdlib/array-uint8' );
var isUnityProbabilityArray = require( '@stdlib/assert-is-unity-probability-array' );
var arr = [ 0.0, 1.0 ];
var bool = isUnityProbabilityArray( arr );
// returns true
arr = [ 0.5, 0.25, 0.25 ];
bool = isUnityProbabilityArray( arr );
// returns true
arr = new Uint8Array( [ 0, 0, 1, 0 ] );
bool = isUnityProbabilityArray( arr );
// returns true
arr = [ 0.4, 0.4, 0.4 ];
bool = isUnityProbabilityArray( arr );
// returns false
arr = [ 3.14, -1.0 ];
bool = isUnityProbabilityArray( arr );
// returns false
bool = isUnityProbabilityArray( [] );
// returns false
bool = isUnityProbabilityArray( null );
// returns false
See Also
-
@stdlib/assert-is-probability
: test if a value is a probability. -
@stdlib/assert-is-probability-array
: test if a value is an array-like object containing only probabilities.
Notice
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.