npm install @stdlib/array-base-where

Alternatively,

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• For use in Observable, or in browser/node environments, use theUniversal Module Definition (UMD) build available on theumd branch (seeREADME).

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To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

varwhere=require('@stdlib/array-base-where');

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 eitherx ory. 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. Ifcondition is non-empty, must be broadcastcompatible with the resolved output array length.
• y: second input array. Ifcondition is 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 eitherx ory. 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. Ifcondition is non-empty, must be broadcastcompatible with the output array.
• y: second input array. Ifcondition is 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

This package is part ofstdlib, 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 developstdlib, see the main projectrepository.

SeeLICENSE.

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