CUSH: Main function for CUSH models

Description Usage Arguments Details Value References See Also

View source: R/CUSH.R

Description

Main function to estimate and validate a CUSH model for ordinal responses, with or without covariates to explain the shelter effect.

Usage

1
CUSH(Formula,data,...)

Arguments

Formula

Object of class Formula.

data

Data frame from which model matrices and response variables are taken.

...

Additional arguments to pass to the fitting procedure. Argument X specifies the matrix of subjects covariates to include in the model for explaining the shelter effect (not including intercept).

Details

The estimation procedure is not iterative, so a null result for CUSH$niter is produced. The optimization procedure is run via "optim". If covariates are included, the variance-covariance matrix is computed as the inverse of the returned numerically differentiated Hessian matrix (option: hessian=TRUE as argument for "optim"). If not positive definite, it returns a warning message and produces a matrix with NA entries.

Value

An object of the class "CUSH" is a list containing the following results:

estimates

Maximum likelihood parameters estimates

loglik

Log-likelihood function at the final estimates

varmat

Variance-covariance matrix of final estimates (if X=0, it returns the square of the estimated standard error for the shelter parameter δ)

BIC

BIC index for the estimated model

References

Capecchi S. and Piccolo D. (2015). Dealing with heterogeneity/uncertainty in sample survey with ordinal data, IFCS Proceedings, University of Bologna
Capecchi S. and Iannario M. (2016). Gini heterogeneity index for detecting uncertainty in ordinal data surveys, Metron - DOI: 10.1007/s40300-016-0088-5

See Also

loglikCUSH


CUB documentation built on May 19, 2017, 4:24 p.m.

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