66 lines
1.4 KiB
JavaScript
66 lines
1.4 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var PINF = require( '@stdlib/constants/float64/pinf' );
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// MAIN //
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/**
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* Computes a chi-square test statistic.
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*
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* @private
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* @param {NonNegativeInteger} N - number of indexed elements
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* @param {Float64Array} x - observation frequencies
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* @param {integer} strideX - `x` stride length
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* @param {Float64Array} y - expected frequencies
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* @param {integer} strideY - `y` stride length
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* @returns {number} test statistic
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*/
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function testStatistic( N, x, strideX, y, strideY ) {
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var stat;
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var v1;
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var v2;
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var d;
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var i;
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stat = 0.0;
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for ( i = 0; i < N; i++ ) {
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v1 = x[ i*strideX ];
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v2 = y[ i*strideY ];
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if ( v2 === 0.0 ) {
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if ( v1 === 0.0 ) {
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continue;
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}
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return PINF;
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}
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d = v1 - v2;
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stat += ( d * d ) / v2;
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}
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return stat;
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}
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// EXPORTS //
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module.exports = testStatistic;
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