apollo_dft {apollo} | R Documentation |
Calculate DFT probabilities
Description
Calculate probabilities of a Decision Field Theory (DFT) with external thresholds.
Usage
apollo_dft(dft_settings, functionality)
Arguments
dft_settings |
List of settings for the DFT model. It should contain the following elements.
-
alternatives: Named numeric vector. Names of alternatives and
their corresponding value in choiceVar .
-
avail: Named list of numeric vectors or scalars. Availabilities
of alternatives, one element per alternative. Names of
elements must match those in alternatives . Values
can be 0 or 1.
-
choiceVar: Numeric vector. Contains choices for all observations.
It will usually be a column from the database. Values
are defined in alternatives .
-
attrValues: A named list with as many elements as alternatives.
Each element is itself a named list of vectors of the
alternative attributes for each observation (usually a
column from the database). All alternatives must have
the same attributes (can be set to zero if not relevant).
-
altStart: A named list with as many elements as alternatives.
Each elment can be a scalar or vector containing the
starting preference value for the alternative.
-
attrWeights: A named list with as many elements as attributes,
or fewer. Each element is the weight of the attribute,
and can be a scalar, a vector with as many elements as
observations, or a matrix/array if random. They should
add up to one for each observation and draw (if present),
and will be re-scaled if they do not. attrWeights
and attrScalings are incompatible, and they should
not be both defined for an attribute. Default is 1 for
all attributes.
-
attrScalings: A named list with as many elements as attributes,
or fewer. Each element is a factor that scale the
attribute, and can be a scalar, a vector or a
matrix/array. They do not need to add up to one
for each observation. attrWeights and
attrScalings are incompatible, and they
should not be both defined for an attribute.
Default is 1 for all attributes.
-
procPars: A list containing the four DFT 'process parameters'
-
error_sd: Numeric scalar or vector. The standard deviation of the the error term in each timestep.
-
timesteps: Numeric scalar or vector. Number of timesteps to consider. Should be an integer bigger than 0.
-
phi1: Numeric scalar or vector. Sensitivity.
-
phi2: Numeric scalar or vector. Process parameter.
-
rows: Boolean vector. Consideration of rows in the likelihood calculation, FALSE to exclude. Length equal to the number of observations (nObs). Default is "all" , equivalent to rep(TRUE, nObs) .
-
componentName: Character. Name given to model component.
|
functionality |
Character. Can take different values depending on desired output.
-
"estimate" : Used for model estimation.
-
"prediction" : Used for model predictions.
-
"validate" : Used for validating input.
-
"zero_LL" : Used for calculating null likelihood.
-
"conditionals" : Used for calculating conditionals.
-
"output" : Used for preparing output after model estimation.
-
"raw" : Used for debugging.
|
Value
The returned object depends on the value of argument functionality
as follows.
-
"estimate"
: vector/matrix/array. Returns the probabilities for the chosen alternative for each observation.
-
"prediction"
: List of vectors/matrices/arrays. Returns a list with the probabilities for all alternatives, with an extra element for the chosen alternative probability.
-
"validate"
: Same as "estimate"
-
"zero_LL"
: vector/matrix/array. Returns the probability of the chosen alternative when all parameters are zero.
-
"conditionals"
: Same as "estimate"
-
"output"
: Same as "estimate"
but also writes summary of input data to internal Apollo log.
-
"raw"
: Same as "prediction"
References
Hancock, T.; Hess, S. and Choudhury, C. (2018) Decision field theory: Improvements to current methodology and comparisons with standard choice modelling techniques. Transportation Research 107B, 18 - 40.
Hancock, T.; Hess, S. and Choudhury, C. (Submitted) An accumulation of preference: two alternative dynamic models for understanding transport choices.
Roe, R.; Busemeyer, J. and Townsend, J. (2001) Multialternative decision field theory: A dynamic connectionist model of decision making. Psychological Review 108, 370
[Package
apollo version 0.2.0
Index]