Functions
def	statistics.nullLoglikelihood (availability, iterator)
	Computes the null log likelihood from the sample and ask Biogeme to include it in the output file. More...

def	statistics.choiceStatistics (choiceSet, choice, iterator)
	Computes the number of times each alternative is chosen in the data set and ask Biogeme to include it in the output file. More...

def	statistics.availabilityStatistics (availability, iterator)
	Computes the number of times each alternative is declared available in the data set and ask Biogeme to include it in the output file. More...

def	statistics.cteLoglikelihood (choiceSet, choice, iterator)
	Computes the constant loglikelihood from the sample and ask Biogeme to include it in the output file. More...

Detailed Description

Function Documentation

def statistics.availabilityStatistics	(	availability,
		iterator
	)

Computes the number of times each alternative is declared available in the data set and ask Biogeme to include it in the output file.

Parameters

availability	Dictionary containing for each alternative the expression for its availability.
iterator	An iterator on the data file.

Returns: A dictionary n with an entry n[i] for each alternative i containing the number of times it is available.

Definition at line 44 of file statistics.py.

def statistics.choiceStatistics	(	choiceSet,
		choice,
		iterator
	)

Computes the number of times each alternative is chosen in the data set and ask Biogeme to include it in the output file.

Parameters

choiceSet	list containing the alternatives for which statistics must be computed.
choice	expression producing the id of the chosen alternative.
iterator	An iterator on the data file.

Returns: A dictionary n with an entry n[i] for each alternative i containing the number of times it is chosen.

Definition at line 30 of file statistics.py.

def statistics.cteLoglikelihood	(	choiceSet,
		choice,
		iterator
	)

Computes the constant loglikelihood from the sample and ask Biogeme to include it in the output file.

It assumes that the full choice set is available for each observation.

Parameters

choiceSet	list containing the alternatives in the choice set.
choice	expression producing the id of the chosen alternative.
iterator	An iterator on the data file.

Returns: log likelihood of a logit model where the only parameters are the alternative specific constants. If is the number of times alternative is chosen, then it is given by
$\mathcal{L} = \sum_i n_i \ln(n_i) - n \ln(n)$
where $n = \sum_i n_i$ is the total number of observations.

Definition at line 60 of file statistics.py.

def statistics.nullLoglikelihood	(	availability,
		iterator
	)

Computes the null log likelihood from the sample and ask Biogeme to include it in the output file.

Parameters

availability	A dictionary mapping each alternative ID with its availability condition.
iterator	An iterator on the data file.

Returns: log likelihood of a model where the choice probability for observation is given by is , where is the number of available alternatives, i.e.
$\mathcal{L} = -\sum_n \ln(J_n)$

Definition at line 13 of file statistics.py.