SORTIE math library. More...

#include <ModelMath.h>

Public Member Functions
	~clModelMath ()

Static Public Member Functions
static float	CalcPointValue (float fX, float fSlope, float fIntercept=0.0)
	Returns the value of a linear function. More...

static float	GetRand ()
	Random number generator. More...

static float	CalculateBasalArea (float fDbh)
	Calculates basal area. More...

static float	Round (float fNumber, int iNumDigits)
	Rounds a number to a specified number of digits. More...

static int	RandomRound (float fNumber)
	Uses a random number to decide whether to round a number up or down to the next integer. More...

static float	CalculateWeibullFunction (float fDispersal, float fTheta, float fDistance)
	Calculates the exponential of the Weibull probability distribution function at a particular point. More...

static float	CalculateLognormalFunction (float fX0, float fXb, float fDistance)
	Calculates the exponential of the Lognormal probability distribution function at a particular point. More...

static int	PoissonRandomDraw (float fLambda)
	Returns a random Poisson-distributed number. More...

static float	LognormalRandomDraw (float fMean, float fStdDev)
	Returns a random lognormally-distributed number. More...

static float	NormalRandomDraw (float fStdDev)
	Returns a random normally-distributed number with mean zero and standard deviation sigma. More...

static int	NegBinomialRandomDraw (float fMean, float fClumping)
	Returns a random negative binomially-distributed number. More...

static float	AddBarkToDBH (float fDIB, float fA, float fB, float fC)
	Adds bark to a tree diameter. More...

static float	InverseGaussianRandomDraw (float fMu, float fLambda)
	Returns a random number over the inverse Gaussian distribution. More...

static float	GammaRandomDraw (float fMean, float fScale)
	Returns a random number drawn from the gamma distribution. More...

static void	SetRandomSeed (long iSeed)
	Sets the random seed. More...

Static Public Attributes
static gsl_rng *	randgen
	Random number generator. More...

Detailed Description

SORTIE math library.

This library provides some model-specific math functions.

The random number generator is very important. To make sure that no one can mess with the seed, I put the seed and the seed setting function in the private portion. Then clSimManager is a friend class and is the only one that can change the seed.

This used to be a library of C-style functions. But it turns out that the random number generator doesn't work right unless the seed is a class member.

I have made some wrappers for GSL, for back-compatibility from before GSL was used. But I have also opened up the random number generator so that other classes can use the GSL functions directly if they wish.

Author: Lora E. Murphy

Edit history:
--------------—
October 20, 2011 - Wiped the slate clean for SORTIE 7.0 (LEM)

Constructor & Destructor Documentation

◆ ~clModelMath()

clModelMath::~clModelMath ( )

inline

Member Function Documentation

◆ AddBarkToDBH()

static float clModelMath::AddBarkToDBH	(	float	fDIB,
		float	fA,
		float	fB,
		float	fC
	)

static

Adds bark to a tree diameter.

The equation is:

DBH = a + b * DIB + c * DIB²

where:

DIB = diameter inside bark at 1.35 meters, in cm
DBH = diameter outside bark at 1.35 meters, in cm
a, b, and c are parameters

Parameters

fDIB	Diameter inside bark at 1.35 meters' height, in cm
fA	"a" term in equation above
fB	"b" term in equation above
fC	"c" term in equation above

Returns: Diameter outside the bark at 1.35 meters' height, in cm

Exceptions

modelErr if DIB is less than or equal to 0, or large enough to create float overflow.

◆ CalcPointValue()

static float clModelMath::CalcPointValue	(	float	fX,
		float	fSlope,
		float	fIntercept = `0.0`
	)

static

Returns the value of a linear function.

Parameters

fX	Point for which to calculate the function.
fSlope	Slope of the function.
fIntercept	Intercept of the function.

Returns: Function value at the given point.

◆ CalculateBasalArea()

static float clModelMath::CalculateBasalArea ( float fDbh )

static

Calculates basal area.

Parameters

fDbh	DBH in cm for which to calculate basal area.

Returns: Basal area in square meters.

Exceptions

modelErr if DBH is less than or equal to 0.

◆ CalculateLognormalFunction()

static float clModelMath::CalculateLognormalFunction	(	float	fX0,
		float	fXb,
		float	fDistance
	)

static

Calculates the exponential of the Lognormal probability distribution function at a particular point.

Parameters

fX0	Value of X₀ variable
fXb	Value of X_b variable
fDistance	Distance, in meters, at which to calculate the function

Returns: Value of function

Exceptions

modelErr if fX0 or fDistance are not greater than 0, or if fXb is zero.

◆ CalculateWeibullFunction()

static float clModelMath::CalculateWeibullFunction	(	float	fDispersal,
		float	fTheta,
		float	fDistance
	)

static

Calculates the exponential of the Weibull probability distribution function at a particular point.

Parameters

fDispersal	Value of dispersal variable
fTheta	Value of theta variable
fDistance	Distance, in meters, at which to calculate the function

Returns: Value of function

◆ GammaRandomDraw()

static float clModelMath::GammaRandomDraw	(	float	fMean,
		float	fScale
	)

static

Returns a random number drawn from the gamma distribution.

This is a wrapper for the GSL function gsl_ran_gamma. For this function, a = shape parameter, and b = scale parameter. The shape parameter a = mean / scale.

Parameters

fMean	Function mean.
fScale	Scale parameter.

Returns: Desired random deviate.

◆ GetRand()

static float clModelMath::GetRand ( )

static

Random number generator.

This just wraps a call to GSL's uniform random number generator.

Returns: a random number between 0 and 1.

◆ InverseGaussianRandomDraw()

static float clModelMath::InverseGaussianRandomDraw	(	float	fMu,
		float	fLambda
	)

static

Returns a random number over the inverse Gaussian distribution.

I got this code from http://www.cbr.washington.edu/node/617, which is the dissertation "Spatial and Temporal Models of Migrating Juvenile Salmon with Applications", by Richard W. Zabel, University of Washington.

The inverse Gaussian PDF is: f(x; μ, λ) = [λ /(2πx³)]^(1/2) * exp[(-λ(x-μ)² )/ (2 μ²x)]

Parameters

fMu	mu.
fLambda	lambda.

◆ LognormalRandomDraw()

static float clModelMath::LognormalRandomDraw	(	float	fMean,
		float	fStdDev
	)

static

Returns a random lognormally-distributed number.

The lognormal distribution has the form

p(x) dx = 1/(x * sqrt(2 pi sigma²)) exp(-(ln(x) - zeta)²/2 sigma²) dx

for x > 0. Lognormal random numbers are the exponentials of gaussian random numbers.

This just wraps the appropriate GSL function.

Parameters

fMean	Mean of the distribution, or zeta in the above formula.
fStdDev	Standard deviation of the distribution, or sigma in the above formula.

Returns: Random lognormally-distributed number.

◆ NegBinomialRandomDraw()

static int clModelMath::NegBinomialRandomDraw	(	float	fMean,
		float	fClumping
	)

static

Returns a random negative binomially-distributed number.

The form of the distribution is from Equation 3.103 from Hilborn and Mangel (The Ecological Detective). Charlie Canham created this code.

Parameters

fMean	Function mean.
fClumping	Clumping parameter.

Returns: Random negative-binomially-distributed number.

◆ NormalRandomDraw()

static float clModelMath::NormalRandomDraw ( float fStdDev )

static

Returns a random normally-distributed number with mean zero and standard deviation sigma.

The probability distribution for normal random variates is, p(x) dx = {1 / sqrt{2 π σ²}} exp (-x² / 2σ²) dx for x in the range -infty to +infty. Use the transformation z = mu + x on the numbers returned to obtain a normal distribution with mean mu.

This function just wraps the appropriate GSL function.

Parameters

fStdDev Standard deviation.

Returns: Random normally-distributed number.

◆ PoissonRandomDraw()

static int clModelMath::PoissonRandomDraw ( float fLambda )

static

Returns a random Poisson-distributed number.

This just wraps the appropriate GSL function.

Parameters

fLambda Lambda (mean) of the Poisson function.

Returns: Integer random draw.

◆ RandomRound()

static int clModelMath::RandomRound ( float fNumber )

static

Uses a random number to decide whether to round a number up or down to the next integer.

The number is split into integer and fractional parts. A random number is compared to the fractional part; if it is less than or equal to it, one is added to the integer part; otherwise the integer part is returned as-is.

Parameters

fNumber Number to round.

Returns: Rounded number.

◆ Round()

static float clModelMath::Round	(	float	fNumber,
		int	iNumDigits
	)

static

Rounds a number to a specified number of digits.

For this function, credit www.codeproject.com.

Parameters

fNumber	Number to round.
iNumDigits	Number of digits to round the number to. If 0, the number is rounded to the nearest integer.

Returns: Rounded number.

◆ SetRandomSeed()

static void clModelMath::SetRandomSeed ( long iSeed )

inlinestatic

Sets the random seed.

This should always be a negative number.

Parameters

iSeed Seed to set.

Member Data Documentation

◆ randgen

gsl_rng* clModelMath::randgen

static

Random number generator.

Currently set to the Mersenne Twister algorithm.

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

ModelMath.h

Public Member Functions

Static Public Member Functions

Static Public Attributes

Detailed Description

Constructor & Destructor Documentation

◆ ~clModelMath()

Member Function Documentation

◆ AddBarkToDBH()

◆ CalcPointValue()

◆ CalculateBasalArea()

◆ CalculateLognormalFunction()

◆ CalculateWeibullFunction()

◆ GammaRandomDraw()

◆ GetRand()

◆ InverseGaussianRandomDraw()

◆ LognormalRandomDraw()

◆ NegBinomialRandomDraw()

◆ NormalRandomDraw()

◆ PoissonRandomDraw()

◆ RandomRound()

◆ Round()

◆ SetRandomSeed()

Member Data Documentation

◆ randgen