Psychometric function that allows for models the variance of the data by a beta distribution. More...

#include <psychometric.h>

Inheritance diagram for BetaPsychometric:

Public Member Functions
	BetaPsychometric (int nAFC, PsiCore core, PsiSigmoid sigmoid)
double	negllikeli (const std::vector< double > &prm, const PsiData *data) const
	negative log likelihood
std::vector< double >	dnegllikeli (const std::vector< double > &prm, const PsiData *data) const
	1st derivative of the negative log likelihood
Matrix *	ddnegllikeli (const std::vector< double > &prm, const PsiData *data) const
	2nd derivative of the negative log likelihood (newly allocated matrix)
unsigned int	getNparams (void) const
	get the number of free parameters of the psychometric function
double	deviance (const std::vector< double > &prm, const PsiData *data) const
	deviance for a given data set and parameter constellation
std::vector< double >	getStart (const PsiData *data) const
	determine a starting value using logistic regression on a dataset

Detailed Description

Psychometric function that allows for models the variance of the data by a beta distribution.

When fitting psychometric functions, we usually assume independence of the responses. Is this independence is violated, the binomial variance model is no longer adequate. The beta psychometric function can better deal with this. It fits an additional parameter nu, such that the subjects responses are distributed according to a beta distribution with parameters alpha = Psi(x)*nu*n+1, beta = (Psi(x)-1)*nu*n+1

Member Function Documentation

Matrix * BetaPsychometric::ddnegllikeli	(	const std::vector< double > &	prm,
		const PsiData *	data
	)			const `[virtual]`

2nd derivative of the negative log likelihood (newly allocated matrix)

Parameters:

	prm	parameters at which the second derivative should be evaluated
	data	data for which the likelihood should be evaluated

Reimplemented from PsiPsychometric.

double BetaPsychometric::deviance	(	const std::vector< double > &	prm,
		const PsiData *	data
	)			const `[virtual]`

deviance for a given data set and parameter constellation

Parameters:

	prm	parameters of the psychometric function model
	data	data for which the likelihood should be evaluated

Reimplemented from PsiPsychometric.

std::vector< double > BetaPsychometric::dnegllikeli	(	const std::vector< double > &	prm,
		const PsiData *	data
	)			const `[virtual]`

1st derivative of the negative log likelihood

Parameters:

	prm	parameters at which the first derivative should be evaluated
	data	data for which the likelihood should be evaluated

Reimplemented from PsiPsychometric.

double BetaPsychometric::negllikeli	(	const std::vector< double > &	prm,
		const PsiData *	data
	)			const `[virtual]`

negative log likelihood

Parameters:

	prm	parameters of the psychometric function model
	data	data for which the likelihood should be evaluated

Reimplemented from PsiPsychometric.

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

src/psychometric.h
src/psychometric.cc

BetaPsychometric Class Reference

Public Member Functions

Detailed Description

Member Function Documentation