com.itemanalysis.psychometrics.irt.estimation

Class ItemParamPriorLogNormal

java.lang.Object

com.itemanalysis.psychometrics.irt.estimation.ItemParamPriorLogNormal

All Implemented Interfaces:

ItemParamPrior

public class ItemParamPriorLogNormal
extends java.lang.Object
implements ItemParamPrior

Implementation of an ItemParamPrior for the LogNormal distribution. This class is a translation of ItemParamPriorLogNormal.cpp in Brad Hanson's ETIRM library, Copyright (c) 2000, Bradley A. Hanson.

Constructor Summary

Constructors

Constructor and Description
ItemParamPriorLogNormal() Constructor for the standard lognormal distribution
ItemParamPriorLogNormal(double[] param) Constructor takes an array as the input parameters.
ItemParamPriorLogNormal(double mean, double sd) Constructor taking the mean and standard deviation as arguments.

Method Summary

Modifier and Type	Method and Description
java.lang.String	distributionName()
int	getNumberOfParameters()
double	logDensity(double p) Only compute part of the log of the density that depends on the parameter
double	logDensityDeriv1(double p) First derivative of log density.
double	logDensityDeriv2(double p) Second derivative of log density.
double	nearestNonZero(double x) If density of x is zero (x <= 0) then return small slightly greater than zero that has a non-zero density
boolean	zeroDensity(double p) Returns true if density at p is zero

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ItemParamPriorLogNormal

public ItemParamPriorLogNormal()

Constructor for the standard lognormal distribution

ItemParamPriorLogNormal

public ItemParamPriorLogNormal(double[] param)

Constructor takes an array as the input parameters. The first element is the mean and the second element is the standard deviation.

Parameters:

param - an array with the meanLog as the first argument and sdLog as the second.

ItemParamPriorLogNormal

public ItemParamPriorLogNormal(double mean,
                               double sd)

Constructor taking the mean and standard deviation as arguments.

Parameters:

mean - mean on the logarithmic scale (i.e. meanLog)

sd - standard deviation on the logarithmic scale (i.e. sdLog)

Method Detail

zeroDensity

public boolean zeroDensity(double p)

Returns true if density at p is zero

Specified by:

zeroDensity in interface ItemParamPrior

Parameters:

p -

Returns:

nearestNonZero

public double nearestNonZero(double x)

If density of x is zero (x <= 0) then return small slightly greater than zero that has a non-zero density

Specified by:

nearestNonZero in interface ItemParamPrior

Parameters:

x -

Returns:

logDensity

public double logDensity(double p)

Only compute part of the log of the density that depends on the parameter

Specified by:

logDensity in interface ItemParamPrior

Parameters:

p - Argument of log density function (an item parameter value)

Returns:

logDensityDeriv1

public double logDensityDeriv1(double p)

First derivative of log density. Only compute part of the log of the density that depends on the parameter.

Specified by:

logDensityDeriv1 in interface ItemParamPrior

Parameters:

p -

Returns:

logDensityDeriv2

public double logDensityDeriv2(double p)

Second derivative of log density. Only compute part of the log of the density that depends on the parameter.

Specified by:

logDensityDeriv2 in interface ItemParamPrior

Parameters:

p -

Returns:

getNumberOfParameters

public int getNumberOfParameters()

Specified by:

getNumberOfParameters in interface ItemParamPrior

distributionName

public java.lang.String distributionName()

Specified by:

distributionName in interface ItemParamPrior