QLSQ Class Reference

#include <quadlsq.h>

Public Member Functions
	QLSQ ()
void	clear ()
void	add (double x, double y)
void	remove (double x, double y)
inT32	count ()
void	fit (int degree)
double	get_a ()
double	get_b ()
double	get_c ()

Detailed Description

Definition at line 25 of file quadlsq.h.

Constructor & Destructor Documentation

QLSQ::QLSQ ( )

inline

Definition at line 28 of file quadlsq.h.

           {  //constructor
      clear();  //set to zeros
    }

Member Function Documentation

void QLSQ::add	(	double	x,
		double	y
	)

Definition at line 56 of file quadlsq.cpp.

                                 {
  n++;                           // Count elements.
  sigx += x;                     // Update accumulators.
  sigy += y;
  sigxx += x * x;
  sigxy += x * y;
  sigyy += y * y;
  sigxxx += static_cast<long double>(x) * x * x;
  sigxxy += static_cast<long double>(x) * x * y;
  sigxxxx += static_cast<long double>(x) * x * x * x;
}

void QLSQ::clear

(

)

Definition at line 34 of file quadlsq.cpp.

                 {  // initialize
  a = 0.0;
  b = 0.0;
  c = 0.0;
  n = 0;                           // No elements.
  sigx = 0.0;                      // Zero accumulators.
  sigy = 0.0;
  sigxx = 0.0;
  sigxy = 0.0;
  sigyy = 0.0;
  sigxxx = 0.0;
  sigxxy = 0.0;
  sigxxxx = 0.0;
}

inT32 QLSQ::count ( )

inline

Definition at line 39 of file quadlsq.h.

                  {  //no of elements
      return n;
    }

void QLSQ::fit

(

int

degree

)

Definition at line 100 of file quadlsq.cpp.

                         {
  long double x_variance = static_cast<long double>(sigxx) * n -
      static_cast<long double>(sigx) * sigx;

  // Note: for computational efficiency, we do not normalize the variance,
  // covariance and cube variance here as they are in the same order in both
  // nominators and denominators. However, we need be careful in value range
  // check.
  if (x_variance < kMinVariance * n * n || degree < 1 || n < 2) {
    // We cannot calculate b reliably so forget a and b, and just work on c.
    a = b = 0.0;
    if (n >= 1 && degree >= 0) {
      c = sigy / n;
    } else {
      c = 0.0;
    }
    return;
  }
  long double top96 = 0.0;       // Accurate top.
  long double bottom96 = 0.0;    // Accurate bottom.
  long double cubevar = sigxxx * n - static_cast<long double>(sigxx) * sigx;
  long double covariance = static_cast<long double>(sigxy) * n -
      static_cast<long double>(sigx) * sigy;

  if (n >= 4 && degree >= 2) {
    top96 = cubevar * covariance;
    top96 += x_variance * (static_cast<long double>(sigxx) * sigy - sigxxy * n);

    bottom96 = cubevar * cubevar;
    bottom96 -= x_variance *
        (sigxxxx * n - static_cast<long double>(sigxx) * sigxx);
  }
  if (bottom96 >= kMinVariance * n * n * n * n) {
    // Denominators looking good
    a = top96 / bottom96;
    top96 = covariance - cubevar * a;
    b = top96 / x_variance;
  } else {
    // Forget a, and concentrate on b.
    a = 0.0;
    b = covariance / x_variance;
  }
  c = (sigy - a * sigxx - b * sigx) / n;
}

double QLSQ::get_a ( )

inline

Definition at line 45 of file quadlsq.h.

                   {  //get x squard
      return a;
    }

double QLSQ::get_b ( )

inline

Definition at line 48 of file quadlsq.h.

                   {  //get x squard
      return b;
    }

double QLSQ::get_c ( )

inline

Definition at line 51 of file quadlsq.h.

                   {  //get x squard
      return c;
    }

void QLSQ::remove	(	double	x,
		double	y
	)

Definition at line 75 of file quadlsq.cpp.

                                    {
  if (n <= 0) {
    tprintf("Can't remove an element from an empty QLSQ accumulator!\n");
    return;
  }
  n--;                           // Count elements.
  sigx -= x;                     // Update accumulators.
  sigy -= y;
  sigxx -= x * x;
  sigxy -= x * y;
  sigyy -= y * y;
  sigxxx -= static_cast<long double>(x) * x * x;
  sigxxy -= static_cast<long double>(x) * x * y;
  sigxxxx -= static_cast<long double>(x) * x * x * x;
}

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The documentation for this class was generated from the following files:

• ccstruct/quadlsq.h
• ccstruct/quadlsq.cpp