apollo_ownModel: Calculates own model probabilities

In apollo: Tools for Choice Model Estimation and Application

Calculates own model probabilities

Description

Receives functions or expressions for each functionality so that a user-defined model can interface with Apollo.

Usage

apollo_ownModel(ownModel_settings, functionality)

Arguments

ownModel_settings

List of arguments. Only likelihood is mandatory. gradient: Function or expression used to calculate the gradient of the likelihood. If not provided, Apollo will attempt to calculate it automatically. likelihood: Function or expression used to calculate the likelihood of the model. Should evaluate to a vector, matrix, or 3-dimensional array. prediction: Function or expression used to calculate the prediction of the model. Should evaluate to a vector, matrix, or 3-dimensional array. report: List of functions or expressions used to produce a text report summarising the input and parameter estimates of the model. Should contain two elements: "data" (with a summary of the input data), and "param" (with a summary of the estimated parameters). shares_LL: Function or expression used to calculate the likelihood of the constants-only model. zero_LL: Function or expression used to calculate the likelihood of the base model (e.g. equiprobable model).

functionality

Character. Setting instructing Apollo what processing to apply to the likelihood function. This is in general controlled by the functions that call apollo_probabilities, though the user can also call apollo_probabilities manually with a given functionality for testing/debugging. Possible values are: "components": For further processing/debugging, produces likelihood for each model component (if multiple components are present), at the level of individual draws and observations. "conditionals": For conditionals, produces likelihood of the full model, at the level of individual inter-individual draws. "estimate": For model estimation, produces likelihood of the full model, at the level of individual decision-makers, after averaging across draws. "gradient": For model estimation, produces analytical gradients of the likelihood, where possible. "output": Prepares output for post-estimation reporting. "prediction": For model prediction, produces probabilities for individual alternatives and individual model components (if multiple components are present) at the level of an observation, after averaging across draws. "preprocess": Prepares likelihood functions for use in estimation. "raw": For debugging, produces probabilities of all alternatives and individual model components at the level of an observation, at the level of individual draws. "report": Prepares output summarising model and choiceset structure. "shares_LL": Produces overall model likelihood with constants only. "validate": Validates model specification, produces likelihood of the full model, at the level of individual decision-makers, after averaging across draws. "zero_LL": Produces overall model likelihood with all parameters at zero.

Value

The returned object depends on the value of argument functionality as follows.

• "components": Same as "estimate"

• "conditionals": Same as "estimate"

• "estimate": vector/matrix/array. Returns the probabilities for the chosen alternative for each observation.

• "gradient": List containing the likelihood and gradient of the model component.

• "output": Same as "estimate" but also writes summary of input data to internal Apollo log.

• "prediction": List of vectors/matrices/arrays. Returns a list with the probabilities for all alternatives, with an extra element for the probability of the chosen alternative.

• "preprocess": Returns a list with pre-processed inputs, based on mnl_settings.

• "validate": Same as "estimate", but it also runs a set of tests to validate the function inputs.

• "raw": Same as "prediction"

• "report": Choice overview

• "shares_LL": vector/matrix/array. Returns the probability of the chosen alternative when only constants are estimated.

• "validate": Same as "estimate"

• "zero_LL": vector/matrix/array. Returns the probability of the chosen alternative when all parameters are zero.

apollo documentation built on Nov. 5, 2025, 5:07 p.m.