help ztpflex

Title

ztpflex -- Zero-truncated Poisson mixture regression

Syntax

ztpflex
depvar
[indepvars]
[if] [in]
[,
options]

where depvar has to be a strictly postive outcome.

irr report incidence-rate ratios

nonadaptive use standard Gauss-Hermite quadrature; default is adaptive quadrature

intpoints(#) choose the number of quadrature points used for the approximation; default is intpoints(30)

noconstant suppress constant term

vce(vcetype) vcetype may be oim, robust, cluster clustvar, or opg

vuong perform Vuong test of ztpflex versus ztnbp

maximize_options control the maximization process; see [R] maximize

bootstrap and jackknife are allowed; see prefix.

Description

ztpflex fits a zero-truncated Poisson model with a more flexible mixing distribution
than ztpnm. The integral is approximated using adaptive Gauss-Hermite quadrature.
Generally, a higher number of quadrature points leads to a more accurate approximation,
but it takes longer to converge. It is highly recommended to check the sensitivity of the results; see
[XT] quadchk.

ztpflex, nonadaptive uses standard Gauss-Hermite quadrature.
Generally, this method is less accurate even if the number of quadrature
points is high.

This program uses ml lf method.

Options

irr reports incidence-rate ratios.

nonadaptive uses standard Gauss-Hermite quadrature; the default is
adaptive quadrature.

intpoints(#) chooses the number of points used for the approximation.
The default is intpoints(30). The maximum is 195. Generally, a higher number of
points leads to a more accurate approximation, but it takes longer to
converge. It is highly recommended to check the sensitivity of the results.

noconstant suppresses the constant term (intercept) in the model.

vce(vcetype) specifies the type of standard error reported, which
includes types that are derived from asymptotic theory, that are robust to
some kinds of misspecification, and that allow for intragroup correlation; see
[R] vce_option.

vuong performs a Vuong test of ztpflex versus ztnbp.

maximize_options: difficult, technique(algorithm_spec),
iterate(#), [no]log, trace,
gradient,
showstep,
hessian,
showtolerance,
tolerance(#),
ltolerance(#), nrtolerance(#),
nonrtolerance, and from(init_specs); see [R] maximize.
These options are seldom used.

difficult is the default.

Remarks for quadcheck

See Remarks in [XT] quadchk.

Author

Helmut Farbmacher

Munich Center for the Economics of Aging (MEA)

Max Planck Society, Germany

farbmacher@mea.mpisoc.mpg.de

Reference

Farbmacher, H. 2012: Extensions of hurdle models for overdispersed count data, Health Economics, forthcoming.

Help: [R] ztp, [R] ztpnm, [R] ztnbp