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Take elements from either one of two arrays depending on a condition.
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stdlib-js/array-base-where
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Take elements from either one of two arrays depending on a condition.
importwherefrom'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-where@deno/mod.js';
You can also import the following named exports from the package:
import{assign}from'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-where@deno/mod.js';
Takes elements from eitherx ory depending on a condition.
varx=[1,2,3,4];vary=[5,6,7,8];varcondition=[true,false,true,false];varz=where(condition,x,y);// returns [ 1, 6, 3, 8 ]
The function supports the following parameters:
- condition: array of values indicating whether to take an element from either
xory. If a condition element is truthy, the function takes a respective element fromx; otherwise, the function takes a respective element fromy. If non-empty, must be broadcastcompatible with the resolved output array length. - x: first input array. If
conditionis non-empty, must be broadcastcompatible with the resolved output array length. - y: second input array. If
conditionis non-empty, must be broadcastcompatible with the resolved output array length.
When all input arrays are non-empty, the function supports broadcasting single-element arrays to the resolved output array length, which is equal to the maximum length of all provided input arrays.
varx=[1,2,3,4];vary=[5];varcondition=[true,false,true,false];varz=where(condition,x,y);// returns [ 1, 5, 3, 5 ]z=where(condition,y,x);// returns [ 5, 2, 5, 4 ]z=where([true],x,y);// returns [ 1, 2, 3, 4 ]z=where([false],x,y);// returns [ 5, 5, 5, 5 ]z=where(condition,[1],y);// returns [ 1, 5, 1, 5 ]
Ifcondition is an empty array, the function returns an empty array.
varx=[1,2,3,4];vary=[5,6,7,8];varcondition=[];varz=where(condition,x,y);// returns []
Takes elements from eitherx ory depending on a condition and assigns the values to elements in a provided output array.
varx=[1,2,3,4];vary=[5,6,7,8];varout=[0,0,0,0];varcondition=[true,false,true,false];vararr=where.assign(condition,x,y,out,1,0);// returns [ 1, 6, 3, 8 ]varbool=(arr===out);// returns true
The function supports the following parameters:
- condition: array of values indicating whether to take an element from either
xory. If a condition element is truthy, the function takes a respective element fromx; otherwise, the function takes a respective element fromy. If non-empty, must be broadcastcompatible with the output array. - x: first input array. If
conditionis non-empty, must be broadcastcompatible with the output array. - y: second input array. If
conditionis non-empty, must be broadcastcompatible with the output array. - out: output array.
- stride: output array stride.
- offset: output array offset.
The function supports broadcasting single-element arrays to the output array length.
varx=[1,2,3,4];vary=[5];varcondition=[true,false,true,false];varout=[0,0,0,0];vararr=where.assign(condition,x,y,out,1,0);// returns [ 1, 5, 3, 5 ]out=[0,0,0,0];arr=where.assign(condition,y,x,out,1,0);// returns [ 5, 2, 5, 4 ]out=[0,0,0,0];arr=where.assign([true],x,y,out,1,0);// returns [ 1, 2, 3, 4 ]out=[0,0,0,0];arr=where.assign([false],x,y,out,1,0);// returns [ 5, 5, 5, 5 ]out=[0,0,0,0];arr=where.assign(condition,[1],y,out,1,0);// returns [ 1, 5, 1, 5 ]
Whencondition is an empty array, the function returns the output array unchanged.
varx=[1,2,3,4];vary=[5,6,7,8];varout=[0,0,0,0];varcondition=[];vararr=where.assign(condition,x,y,out,1,0);// returns [ 0, 0, 0, 0 ]varbool=(arr===out);// returns true
importdiscreteUniformfrom'https://cdn.jsdelivr.net/gh/stdlib-js/random-array-discrete-uniform@deno/mod.js';importbernoullifrom'https://cdn.jsdelivr.net/gh/stdlib-js/random-array-bernoulli@deno/mod.js';importwherefrom'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-where@deno/mod.js';varopts={'dtype':'generic'};// Generate an array of indicator values:varcondition=bernoulli(20,0.9,opts);console.log(condition);// Generate an array of random values:varx=discreteUniform(condition.length,0,10,opts);console.log(x);// Define an array containing a broadcasted "missing" value:vary=[NaN];// Return an array with randomly placed missing values:varz=where(condition,x,y);console.log(z);
This package is part ofstdlib, 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 developstdlib, see the main projectrepository.
SeeLICENSE.
Copyright © 2016-2025. The StdlibAuthors.
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