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About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

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countIfs

NPM version Build Status Coverage Status

Perform element-wise evaluation of one or more input arrays according to provided predicate functions and count the number of elements for which all predicates respectively return true.

Usage

import countIfs from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-count-ifs@esm/index.mjs';

countIfs( x0, predicate0[, x1, predicate1[, x2, predicate2[, ...args]] )

Performs element-wise evaluation of one or more input arrays according to provided predicate functions and counts the number of elements for which all predicates respectively return true.

function predicate0( value ) {
    return ( value > 0 );
}

function predicate1( value ) {
    return ( value < 3 );
}

var x0 = [ 0, 1, 0, 1, 2 ];
var x1 = [ 2, 3, 1, 2, 5 ];

var out = countIfs( x0, predicate0, x1, predicate1 );
// returns 1

The function has the following parameters:

  • x0: first input array.
  • predicate0: first predicate function.
  • x1: second input array (optional).
  • predicate1: second predicate function (optional).
  • x2: third input array (optional).
  • predicate2: third predicate function (optional).
  • args: additional input arrays and corresponding predicate functions (optional).

Each predicate function is provided three arguments:

  • value: current array element.
  • index: current array element index.
  • arr: the corresponding input array.

Notes

  • The function assumes that all input arrays have the same length.
  • The function supports array-like objects supporting the accessor protocol (e.g., Complex128Array, Complex64Array, etc).

Examples

<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">

import discreteUniform from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-array-discrete-uniform@esm/index.mjs';
var isPositiveInteger = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/assert-is-positive-integer' ).isPrimitive;
var isNegativeInteger = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/assert-is-negative-integer' ).isPrimitive;
import naryFunction from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-nary-function@esm/index.mjs';
import countIfs from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-count-ifs@esm/index.mjs';

var x = discreteUniform( 10, -5, 5, {
    'dtype': 'int32'
});
console.log( x );

var y = discreteUniform( 10, -5, 5, {
    'dtype': 'int32'
});
console.log( y );

var out = countIfs( x, naryFunction( isPositiveInteger, 1 ), y, naryFunction( isNegativeInteger, 1 ) );
console.log( out );

</script>
</body>
</html>

Notice

This package is part of stdlib, a standard library 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.

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License

See LICENSE.

Copyright

Copyright © 2016-2025. The Stdlib Authors.