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help for ztg                                                     (Joseph Hilbe)
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Zero-Truncated Geometric regression

        ztg  depvar [varlist] [if exp] [in range] [, offset(varname)
             exposure(varname) cluster(varname) level(#) from(asis) irr
             robust nolog maximize_options survey_options]




    aweights, fweights, iweights, and pweights are allowed; see help weights.

    ztg provides access to all maximize options; see help maximize.

    ztg provides access to all survey options; see help svy.


Description

    ztg fits a maximum-likelihood zero-truncated geometric regression model
    of depvar on indepvars, where depvar is a positive count variable.

    ztg acccepts all of the help maximize options, the constraint() option,
    and all survey options and capabilities documented in [SVY]; including
    multi-level surveys; poststratification; and BRR, jackknife, and
    linearization VCE estimators.

    This program uses ml lf method.


Options

        +-------+
    ----+ Model +------------------------------------------------------------

    offset(varname) specifies a varname in model with coefficient constrained
        to 1.

    exposure(varname) specifies a ln(varname) in model with coefficient
        constrained to 1.

    constraints(constraints) apply specified linear constraints.



        +-----------+
    ----+ SE/Robust +--------------------------------------------------------

    cluster(varname)

    robust specifies that the Huber/White/sandwich estimator of variance is
        to be used in place of the traditional calculation.  robust combined
        with cluster() allows observations which are not independent within
        cluster (although they must be independent between clusters).  If you
        specify pweights, robust is implied.

    vce(options) allowed. vce() supports robust, opg, and native.  vce does
        not support options bootstrap or jacknife, However, ztg does support
        the bootstrap and jacknife commands, so these modeling capabilities
        are allowed.


        +-----------+
    ----+ Reporting +--------------------------------------------------------
   
    level(#) specifies the confidence level, in percent, for confidence
        intervals of the coefficients; see help level.

    nolog suppresses the iteration log.


        +-------------+
    ----+ max options +------------------------------------------------------


    maximize_options: technique(algorithm_spec), [no]log, trace, hessian,
        gradient, showstep, shownrtolerance, difficult, iterate(#),
        tolerance(#), ltolerance(#), gtolerance(#), nrtolerance(#),
        nonrtolerance, from(init_specs); see maximize.


        +-------------+
    ----+ svy options +------------------------------------------------------

    survey_options are all available. See help svy




Author and support

    Joseph Hilbe, Arizona State University:  jhilbe@aol.com


Remarks

    ztg is a user authored program. Support is by author. ztg is one of a
    suite of count regression programs created by the author. 2Oct2005

    ztg requires a response with counts 1 and greater.


Examples

    . ztg los hmo white type2 type3, nolog irr

    . ztg los hmo white type2 type3, nolog exposure(pop) cluster(state)

    . bootstrap: ztg los hmo white type2 type3, nolog irr