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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' );
// MAIN //
/**
* Computes the maximum value of a strided array, ignoring `NaN` values.
*
* @param {PositiveInteger} N - number of indexed elements
* @param {NumericArray} x - input array
* @param {integer} stride - stride length
* @param {NonNegativeInteger} offset - starting index
* @returns {number} maximum value
*
* @example
* var floor = require( '@stdlib/math/base/special/floor' );
*
* var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0, NaN, NaN ];
* var N = floor( x.length / 2 );
*
* var v = nanmax( N, x, 2, 1 );
* // returns 4.0
*/
function nanmax( N, x, stride, offset ) {
var max;
var ix;
var v;
var i;
if ( N <= 0 ) {
return NaN;
}
if ( N === 1 || stride === 0 ) {
return x[ offset ];
}
ix = offset;
for ( i = 0; i < N; i++ ) {
v = x[ ix ];
if ( v === v ) {
break;
}
ix += stride;
}
if ( i === N ) {
return NaN;
}
max = v;
i += 1;
for ( i; i < N; i++ ) {
ix += stride;
v = x[ ix ];
if ( isnan( v ) ) {
continue;
}
if ( v > max || ( v === max && isPositiveZero( v ) ) ) {
max = v;
}
}
return max;
}
// EXPORTS //
module.exports = nanmax;
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