etirm::ItemParamPriorNormal Class Reference

Class derived from ItemParamPrior representing a normal prior distribution of item parameters for use in Bayes modal estimation. More...

#include <ItemParamPriorNormal.h>

Inheritance diagram for etirm::ItemParamPriorNormal:

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Collaboration diagram for etirm::ItemParamPriorNormal:

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List of all members.

Public Member Functions
	ItemParamPriorNormal ()
	Default constructor - assigns uniform distribution.
	ItemParamPriorNormal (RealVector &param)
	Constructor taking vector of parameters.
	ItemParamPriorNormal (Real mean, Real sd)
	Constructor taking mean and standard deviation as arguments.
virtual int	NumParameters ()
	Returns number of prior Normal distribution parameters for the IRT item.
virtual Real	LogDensity (Real p)
	Returns log-density of p.
virtual Real	DerivLogDensity1 (Real p)
	Returns first derivative of log density.
virtual Real	DerivLogDensity2 (Real p)
	Returns second derivative of log density.
virtual std::string	DistributionName () const
	Returns string containing name of distribution used for prior.
Private Attributes
Real	variance
	Variance of Normal distribution.

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Detailed Description

Class derived from ItemParamPrior representing a normal prior distribution of item parameters for use in Bayes modal estimation.

Definition at line 40 of file ItemParamPriorNormal.h.

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Constructor & Destructor Documentation

etirm::ItemParamPriorNormal::ItemParamPriorNormal

(

)

Default constructor - assigns uniform distribution.

Definition at line 80 of file ItemParamPriorNormal.cpp.

References etirm::ItemParamPrior::mParameters, and variance.

                                             :
    ItemParamPrior(2)
  {
    mParameters[0] = 0.0;
    mParameters[1] = 1.0;

    variance = 1.0;
  }

etirm::ItemParamPriorNormal::ItemParamPriorNormal

(

RealVector &

param

)

Constructor taking vector of parameters.

Parameters:

[in]

&param

Parameter vector of length 2: param[0] = Normal prior mean, param[1] = Normal prior standard deviation.

Note: The second element of param is the standard deviation, NOT the variance.

Definition at line 49 of file ItemParamPriorNormal.cpp.

References variance.

                                                              :
    ItemParamPrior(param)
  {
    variance = param(2) * param(2);
  }

etirm::ItemParamPriorNormal::ItemParamPriorNormal	(	Real	mean,
		Real	sd
	)

Constructor taking mean and standard deviation as arguments.

Parameters:

[in]	mean	Normal prior mean.
[in]	sd	Normal prior standard deviation.

Note: The second parameter is the standard deviation, NOT the variance.

Definition at line 64 of file ItemParamPriorNormal.cpp.

References etirm::ItemParamPrior::mParameters, and variance.

                                                               :
    ItemParamPrior(2)
  {
    if (sd <= 0.0)
      throw RuntimeError("Invalid s.d. for normal prior",
          "ItemParamPriorNormal::ItemParamPriorNormal");

    mParameters[0] = mean;
    mParameters[1] = sd;

    variance = sd * sd;
  }

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Member Function Documentation

virtual int etirm::ItemParamPriorNormal::NumParameters

(

)

[inline, virtual]

Returns number of prior Normal distribution parameters for the IRT item.

Implements etirm::ItemParamPrior.

Definition at line 49 of file ItemParamPriorNormal.h.

    {
      return 2;
    }

Real etirm::ItemParamPriorNormal::LogDensity

(

Real

p

)

[virtual]

Returns log-density of p.

Parameters:

[in]

p

Argument of log density function (an item parameter value).

Note: Returns only the part of the log of the density that depends on the parameter.

Implements etirm::ItemParamPrior.

Definition at line 97 of file ItemParamPriorNormal.cpp.

References etirm::ItemParamPrior::mParameters, and variance.

  {
    Real value = p - mParameters[0];
    value *= value;
    value /= -2.0 * variance;

    return value;
  }

Real etirm::ItemParamPriorNormal::DerivLogDensity1

(

Real

p

)

[virtual]

Returns first derivative of log density.

Parameters:

[in]

p

Argument of log density function (an item parameter value).

Note: Returns only the part of the log of the density that depends on the parameter.

Implements etirm::ItemParamPrior.

Definition at line 114 of file ItemParamPriorNormal.cpp.

References etirm::ItemParamPrior::mParameters, and variance.

  {
    return -(p - mParameters[0])/variance;
  }

Real etirm::ItemParamPriorNormal::DerivLogDensity2

(

Real

p

)

[virtual]

Returns second derivative of log density.

Parameters:

[in]

p

Argument of log density function (an item parameter value).

Note: Returns 0nly the part of the log of the density that depends on the parameter.

Implements etirm::ItemParamPrior.

Definition at line 127 of file ItemParamPriorNormal.cpp.

References variance.

  {
    return -1.0/variance;
  }

virtual std::string etirm::ItemParamPriorNormal::DistributionName

(

)

const [inline, virtual]

Returns string containing name of distribution used for prior.

Implements etirm::ItemParamPrior.

Definition at line 63 of file ItemParamPriorNormal.h.

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Member Data Documentation

Real etirm::ItemParamPriorNormal::variance [private]

Variance of Normal distribution.

Definition at line 73 of file ItemParamPriorNormal.h.

Referenced by DerivLogDensity1(), DerivLogDensity2(), ItemParamPriorNormal(), and LogDensity().

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

• C:/programs/etirm/src/ItemParamPriorNormal.h
• C:/programs/etirm/src/ItemParamPriorNormal.cpp

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