125 lines
3.5 KiB
JavaScript
125 lines
3.5 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2021 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 isPlainObject = require( '@stdlib/assert/is-plain-object' );
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var setReadOnly = require( '@stdlib/utils/define-read-only-property' );
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var anova1 = require( './../../anova1' );
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var absMeanDiff = require( './absdiff.js' );
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var validate = require( './validate.js' );
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var unique = require( './unique.js' );
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var print = require( './print.js' ); // eslint-disable-line stdlib/no-redeclare
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// MAIN //
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/**
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* Computes Levene's test for equal variances.
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*
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* @param {...NumericArray} arguments - either two or more number arrays or a single numeric array if provided an array of group indicators
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* @param {Options} [options] - function options
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* @param {number} [options.alpha=0.05] - significance level
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* @param {Array} [options.groups] - array of group indicators
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* @throws {TypeError} must provide array-like arguments
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* @throws {RangeError} alpha option must be a number on the interval `[0,1]`
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* @throws {Error} must provide at least two array-like arguments if `groups` is not provided
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* @throws {TypeError} options must be an object
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* @throws {TypeError} must provide valid options
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* @returns {Object} test results
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*
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* @example
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* // Data from Hollander & Wolfe (1973), p. 116:
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* var x = [ 2.9, 3.0, 2.5, 2.6, 3.2 ];
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* var y = [ 3.8, 2.7, 4.0, 2.4 ];
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* var z = [ 2.8, 3.4, 3.7, 2.2, 2.0 ];
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*
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* var out = levene( x, y, z );
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* // returns {...}
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*/
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function levene() {
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var options;
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var result;
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var groups;
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var levels;
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var args;
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var opts;
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var arg;
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var err;
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var out;
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var i;
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var j;
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var k;
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k = arguments.length;
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args = [];
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opts = {};
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if ( isPlainObject( arguments[ k-1 ] ) ) {
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options = arguments[ k-1 ];
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k -= 1;
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err = validate( opts, options );
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if ( err ) {
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throw err;
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}
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} else {
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options = {};
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}
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if ( opts.groups ) {
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args = arguments[ 0 ];
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groups = opts.groups;
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levels = unique( groups );
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k = levels.length;
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if ( k < 2 ) {
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throw new Error( 'invalid option. `groups` option must contain at least two unique elements. Value: `' + levels + '`.' );
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}
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} else {
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groups = [];
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args = [];
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levels = [];
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for ( i = 0; i < k; i++ ) {
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arg = arguments[ i ];
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if ( arg.length === 0 ) {
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throw new Error( 'invalid argument. Provided arrays cannot be empty. Value: `' + arg + '`.' );
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}
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args = args.concat( arg );
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for ( j = 0; j < arg.length; j++ ) {
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groups.push( i );
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}
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levels.push( i );
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}
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}
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args = absMeanDiff( args, groups, levels );
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result = anova1( args, groups, options );
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out = {};
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setReadOnly( out, 'rejected', result.rejected );
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setReadOnly( out, 'alpha', result.alpha );
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setReadOnly( out, 'pValue', result.pValue );
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setReadOnly( out, 'statistic', result.statistic );
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setReadOnly( out, 'df', [ result.treatment.df, result.error.df ] );
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setReadOnly( out, 'method', 'Levene\'s test for Homogeneity of Variance' );
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setReadOnly( out, 'print', print );
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return out;
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}
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// EXPORTS //
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module.exports = levene;
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