All files / strided/nanmax-by/lib ndarray.js

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/**
* @license Apache-2.0
*
* Copyright (c) 2020 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
 
'use strict';
 
// MODULES //
 
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var isPositiveZero = require( '@stdlib/math/base/assert/is-positive-zero' );
var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
var accessors = require( './accessors.js' );
 
 
// MAIN //
 
/**
* Computes the maximum value of a strided array via a callback function, ignoring `NaN` values.
*
* @param {PositiveInteger} N - number of indexed elements
* @param {Collection} x - input array
* @param {integer} strideX - index increment
* @param {NonNegativeInteger} offsetX - starting index
* @param {Callback} clbk - callback
* @param {*} [thisArg] - execution context
* @returns {number} maximum value
*
* @example
* var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, NaN, 0.0, -1.0, -3.0 ];
*
* function accessor( v ) {
*     return v * 2.0;
* }
*
* var v = nanmaxBy( x.length, x, 1, 0, accessor );
* // returns 8.0
*/
function nanmaxBy( N, x, strideX, offsetX, clbk, thisArg ) {
	var max;
	var ix;
	var o;
	var v;
	var i;

	if ( N <= 0 ) {
		return NaN;
	}
	o = arraylike2object( x );
	if ( o.accessorProtocol ) {
		return accessors( N, o, strideX, offsetX, clbk, thisArg );
	}
	if ( N === 1 || strideX === 0 ) {
		v = clbk.call( thisArg, x[ offsetX ], 0, offsetX, x );
		if ( v === void 0 ) {
			return NaN;
		}
		return v;
	}
	ix = offsetX;
	for ( i = 0; i < N; i++ ) {
		max = clbk.call( thisArg, x[ ix ], i, ix, x );
		if ( max === max && max !== void 0 ) {
			break;
		}
		ix += strideX;
	}
	if ( i === N ) {
		return NaN;
	}
	i += 1;
	for ( i; i < N; i++ ) {
		ix += strideX;
		v = clbk.call( thisArg, x[ ix ], i, ix, x );
		if ( v === void 0 || isnan( v ) ) {
			continue;
		}
		if ( v > max || ( v === max && isPositiveZero( v ) ) ) {
			max = v;
		}
	}
	return max;
}
 
 
// EXPORTS //
 
module.exports = nanmaxBy;