59 lines
1.3 KiB
JavaScript
59 lines
1.3 KiB
JavaScript
|
/**
|
||
|
|
* @license Apache-2.0
|
||
|
|
*
|
||
|
|
* Copyright (c) 2018 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 abs = require( '@stdlib/math/base/special/abs' );
|
||
|
|
var isnan = require( '@stdlib/assert/is-nan' );
|
||
|
|
var pow = require( '@stdlib/math/base/special/pow' );
|
||
|
|
|
||
|
|
|
||
|
|
// MAIN //
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Computes the Triweight kernel for a value.
|
||
|
|
*
|
||
|
|
* @private
|
||
|
|
* @param {number} u - value for which we wish to calculate the Triweight kernel
|
||
|
|
* @returns {number} the value for the kernel at u
|
||
|
|
*
|
||
|
|
* @example
|
||
|
|
* var u = 5;
|
||
|
|
* out = triweight(u); // returns 0
|
||
|
|
*/
|
||
|
|
function triweight(u) {
|
||
|
|
var absU;
|
||
|
|
|
||
|
|
if (isnan(u)) {
|
||
|
|
return NaN;
|
||
|
|
}
|
||
|
|
|
||
|
|
absU = abs(u);
|
||
|
|
if (absU > 1) {
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
return (35 / 32) * pow(1.0 - pow(u, 2.0), 3.0);
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
// EXPORTS //
|
||
|
|
|
||
|
|
module.exports = triweight;
|