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help for tpoisson                                                (Joseph Hilbe)
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Truncated Poisson regression

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

        Note: the option trunc must be included in the command. A trunc
        variable must use the following numbers to indicate the type of
        truncation: 0 = left truncated, 1 = not truncated, -1 = right
        truncated.

        Note: Type value of left truncated site in tleft().

              Type value of right truncated site in tright().

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

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

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


Description

    tpoisson fits a truncated Poisson maximum-likelihood regression of depvar
    on indepvars, where depvar is a non-negative count variable.  The trunc
    option is required. If no observations are truncated, a trunc variable
    with all 1's must be specified. Interpret parameter estimates as one
    would poisson.

    Values on either side of the site of truncation are revalued to the 
    value of the trunc value.

    tpoisson accepts 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 +------------------------------------------------------------

    trunc(truncvar) is required. Values of 1 indicate a non-truncated, 0 a
        left truncated, and -1 a right truncated observation. truncvar may be
        numeric or a variable.

    tleft(#) for left truncation site; tright(#) for right truncation site

    trunc(1) and no tleft or tright values declared is a standard Poisson
        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, tpoisson 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:  hilbe@asu.edu


Remarks

    tpoisson is a user authored program. Support is by author. See Hilbe,
    Negative Binomial Regression, Cambridge University Press, for discussion.
    Related information can also be obtained at [R] poisson. Or see cpoisson
    or cpoissone


Examples
 Before example 1
. gen byte truncvar = 1
. replace truncvar = 0 if time<=3

    . tpoisson time hmo age, trunc(truncvar) tle(3) nolog irr

 Before example 2
 . replace truncvar = 1
 . replace truncvar = 0 if time<=2
 . replace truncvar = -1 if time >=30

    . tpoisson time hmo age, trunc(truncvar) tleft(2) tright(30) nolog
        cluster(provnum)

    . bootstrap: tpoisson deaths smokes a2-a5, trunc(truncvar) tright(10)
        exposure(pyears) irr nolog

    . svyset psuid [pweight=finalwgt], strata(stratid)

    . svy: tpoisson zinc age age2 weight female black orace rural, trunc(cv)
        tright(20) nolog irr


Also see

    Manual:  [R] Poisson regression; [SVY] Svy: poisson

    Online:  help cpoisson cpoissone  poisson