Skip to content

Files

Latest commit

stdlib-botstdlib-bot
Auto-generated commit
Sep 27, 2022
b5471f7 · Sep 27, 2022

History

History

is-unity-probability-array

Folders and files

NameName
Last commit message
Last commit date

parent directory

..
benchmark
benchmark
Sep 26, 2022
docs
docs
Sep 27, 2022
examples
examples
May 5, 2021
lib
lib
Sep 23, 2022
test
test
Jul 10, 2021
README.md
README.md
Sep 7, 2021
package.json
package.json
May 5, 2021

README.md

isUnityProbabilityArray

Test if a value is an array of probabilities that sum to one.

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) and sqrt(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