All files scorr.js

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/**
* @license Apache-2.0
*
* Copyright (c) 2026 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 max = require( '@stdlib/math/base/special/max' );
var min = require( '@stdlib/math/base/special/min' );
var sqrt = require( '@stdlib/math/base/special/sqrt' );
var rankData = require( './ranks.js' );
 
 
// MAIN //
 
/**
* Computes the Spearman rank correlation coefficient between `x` and `y`.
*
* @private
* @param {NumericArray} x - first data array
* @param {NumericArray} y - second data array
* @returns {Object} object containing the correlation coefficient and the ranks
*
* @example
* var x = [ 1.0, 2.0, 3.0, 4.0 ];
* var y = [ 1.0, 3.0, 2.0, 4.0 ];
* var out = scorr( x, y );
* // returns { rs: ~0.8, xRanks: [...], yRanks: [...] }
*/
function scorr( x, y ) {
	var xRanks;
	var yRanks;
	var xmean;
	var ymean;
	var denom;
	var num;
	var out;
	var xv;
	var yv;
	var n;
	var i;
 
	n = x.length;
 
	// Compute ranks:
	xRanks = rankData( x );
	yRanks = rankData( y );
 
	// Compute Pearson correlation on the ranks:
	xmean = 0.0;
	ymean = 0.0;
	for ( i = 0; i < n; i++ ) {
		xmean += xRanks[ i ];
		ymean += yRanks[ i ];
	}
	xmean /= n;
	ymean /= n;
 
	num = 0.0;
	xv = 0.0;
	yv = 0.0;
	for ( i = 0; i < n; i++ ) {
		num += ( xRanks[ i ] - xmean ) * ( yRanks[ i ] - ymean );
		xv += ( xRanks[ i ] - xmean ) * ( xRanks[ i ] - xmean );
		yv += ( yRanks[ i ] - ymean ) * ( yRanks[ i ] - ymean );
	}
	denom = sqrt( xv ) * sqrt( yv );
 
	out = {};
	out.rs = ( denom === 0.0 ) ? 0.0 : max( min( num / denom, 1.0 ), -1.0 );
	out.xRanks = xRanks;
	out.yRanks = yRanks;
	return out;
}
 
 
// EXPORTS //
 
module.exports = scorr;