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<?php

/*=======================================================================

// File:	JPGRAPH_REGSTAT.PHP

// Description: Regression and statistical analysis helper classes

// Created: 	2002-12-01

// Ver:		$Id: jpgraph_regstat.php 781 2006-10-08 08:07:47Z ljp $

//

// Copyright (c) Aditus Consulting. All rights reserved.

//========================================================================

*/

//------------------------------------------------------------------------

// CLASS Spline

// Create a new data array from an existing data array but with more points.

// The new points are interpolated using a cubic spline algorithm

//------------------------------------------------------------------------

class Spline {

    // 3:rd degree polynom approximation

    private $xdata,$ydata;   // Data vectors

    private $y2;		 // 2:nd derivate of ydata

    private $n=0;

    function Spline($xdata,$ydata) {

	$this->y2 = array();

	$this->xdata = $xdata;

	$this->ydata = $ydata;

	$n = count($ydata);

	$this->n = $n;

	if( $this->n !== count($xdata) ) {

	    JpGraphError::RaiseL(19001);

//('Spline: Number of X and Y coordinates must be the same');

	}

	// Natural spline 2:derivate == 0 at endpoints

	$this->y2[0]    = 0.0;

	$this->y2[$n-1] = 0.0;

	$delta[0] = 0.0;

	// Calculate 2:nd derivate

	for($i=1; $i < $n-1; ++$i) {

	    $d = ($xdata[$i+1]-$xdata[$i-1]);

	    if( $d == 0  ) {

		JpGraphError::RaiseL(19002);

//('Invalid input data for spline. Two or more consecutive input X-values are equal. Each input X-value must differ since from a mathematical point of view it must be a one-to-one mapping, i.e. each X-value must correspond to exactly one Y-value.');

	    }

	    $s = ($xdata[$i]-$xdata[$i-1])/$d;

	    $p = $s*$this->y2[$i-1]+2.0;

	    $this->y2[$i] = ($s-1.0)/$p;

	    $delta[$i] = ($ydata[$i+1]-$ydata[$i])/($xdata[$i+1]-$xdata[$i]) -

		         ($ydata[$i]-$ydata[$i-1])/($xdata[$i]-$xdata[$i-1]);

	    $delta[$i] = (6.0*$delta[$i]/($xdata[$i+1]-$xdata[$i-1])-$s*$delta[$i-1])/$p;

	}

	// Backward substitution

	for( $j=$n-2; $j >= 0; --$j ) {

	    $this->y2[$j] = $this->y2[$j]*$this->y2[$j+1] + $delta[$j];

	}

    }

    // Return the two new data vectors

    function Get($num=50) {

	$n = $this->n ;

	$step = ($this->xdata[$n-1]-$this->xdata[0]) / ($num-1);

	$xnew=array();

	$ynew=array();

	$xnew[0] = $this->xdata[0];

	$ynew[0] = $this->ydata[0];

	for( $j=1; $j < $num; ++$j ) {

	    $xnew[$j] = $xnew[0]+$j*$step;

	    $ynew[$j] = $this->Interpolate($xnew[$j]);

	}

	return array($xnew,$ynew);

    }

    // Return a single interpolated Y-value from an x value

    function Interpolate($xpoint) {

	$max = $this->n-1;

	$min = 0;

	// Binary search to find interval

	while( $max-$min > 1 ) {

	    $k = ($max+$min) / 2;

	    if( $this->xdata[$k] > $xpoint )

		$max=$k;

	    else

		$min=$k;

	}

	// Each interval is interpolated by a 3:degree polynom function

	$h = $this->xdata[$max]-$this->xdata[$min];

	if( $h == 0  ) {

	    JpGraphError::RaiseL(19002);

//('Invalid input data for spline. Two or more consecutive input X-values are equal. Each input X-value must differ since from a mathematical point of view it must be a one-to-one mapping, i.e. each X-value must correspond to exactly one Y-value.');

	}

	$a = ($this->xdata[$max]-$xpoint)/$h;

	$b = ($xpoint-$this->xdata[$min])/$h;

	return $a*$this->ydata[$min]+$b*$this->ydata[$max]+

	     (($a*$a*$a-$a)*$this->y2[$min]+($b*$b*$b-$b)*$this->y2[$max])*($h*$h)/6.0;

    }

}

//------------------------------------------------------------------------

// CLASS Bezier

// Create a new data array from a number of control points

//------------------------------------------------------------------------

class Bezier {

/**

 * @author Thomas Despoix, openXtrem company

 * @license released under QPL

 * @abstract Bezier interoplated point generation,

 * computed from control points data sets, based on Paul Bourke algorithm :

 * http://astronomy.swin.edu.au/~pbourke/curves/bezier/

 */

    private $datax = array();

    private $datay = array();

    private $n=0;

    function Bezier($datax, $datay, $attraction_factor = 1) {

	// Adding control point multiple time will raise their attraction power over the curve

	$this->n = count($datax);

	if( $this->n !== count($datay) ) {

	    JpGraphError::RaiseL(19003);

//('Bezier: Number of X and Y coordinates must be the same');

	}

	$idx=0;

	foreach($datax as $datumx) {

	    for ($i = 0; $i < $attraction_factor; $i++) {

		$this->datax[$idx++] = $datumx;

	    }

	}

   	$idx=0;

	foreach($datay as $datumy) {

	    for ($i = 0; $i < $attraction_factor; $i++) {

		$this->datay[$idx++] = $datumy;

	    }

	}

	$this->n *= $attraction_factor;

    }

    function Get($steps) {

	$datax = array();

	$datay = array();

	for ($i = 0; $i < $steps; $i++) {

	    list($datumx, $datumy) = $this->GetPoint((double) $i / (double) $steps);

	    $datax[] = $datumx;

	    $datay[] = $datumy;

	}

	$datax[] = end($this->datax);

	$datay[] = end($this->datay);

	return array($datax, $datay);

    }

    function GetPoint($mu) {

	$n = $this->n - 1;

	$k = 0;

	$kn = 0;

	$nn = 0;

	$nkn = 0;

	$blend = 0.0;

	$newx = 0.0;

	$newy = 0.0;

	$muk = 1.0;

	$munk = (double) pow(1-$mu,(double) $n);

	for ($k = 0; $k <= $n; $k++) {

	    $nn = $n;

	    $kn = $k;

	    $nkn = $n - $k;

	    $blend = $muk * $munk;

	    $muk *= $mu;

	    $munk /= (1-$mu);

	    while ($nn >= 1) {

		$blend *= $nn;

		$nn--;

		if ($kn > 1) {

		    $blend /= (double) $kn;

		    $kn--;

		}

		if ($nkn > 1) {

		    $blend /= (double) $nkn;

		    $nkn--;

		}

	    }

	    $newx += $this->datax[$k] * $blend;

	    $newy += $this->datay[$k] * $blend;

	}

	return array($newx, $newy);

    }

}

// EOF

?>