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help for ddirifit
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Displaying discrete changes and marginal effects from dirifit output

        ddirifit [, at(variables_and_values) iterate(#) ]


Description

    ddirifit displays the change in predicted dependent variable for three
    types of discrete changes in explanatory variable and the marginal
    effects:


        Discrete Changes

        Min --> Max shows the change in predicted dependent variable when the
        explanatory variable changes from its minimum value to its maximum
        value, while keeping all other explanatory variables at their
        specified values (by default the mean). This is the only effect shown
        for dummy variables (variables with only two distinct values).

        +-SD/2 shows the change in predicted dependent variable when the
        explanatory variable moves from half a standard deviation below its
        specified value (by default the mean) to half a standard deviation
        above its specified value, while keeping all other variables at their
        specified values. In other words: It shows the effect of a standard
        deviation change in explanatory variable, centered around the
        specified value, on the predicted dependent variable.

        +-1/2 shows the change in predicted dependent variable when the
        explanatory variable moves from half a unit below its specified value
        to half a unit above its specified value, while keeping all other
        variables at their specified values. In other words: It shows the
        effect of a unit change in explanatory variable, centered around the
        specified value, on the predicted dependent variable.


        Marginal Effects

        MFX at x shows the marginal effect of each (non dummy) variable,
        while keeping all variables at their specified values. The marginal
        effect is the change in predicted dependent variable for a unit
        change in the explanatory variable, assuming that the effect doesn't
        change over that interval.

    ddirifit is only allowed after dirifit in the alternative
    parameterization, i.e. if one or more of muvar(), mu1|2|3|...|k(),
    baseoutcome(), and phivar() is specified or if the alternative option is
    specified.

Options

    at(variables_and_values) allow the user to specify at which values of the
        explanatory variables the effects are calculated.
        variables_and_values is an alternating list of variables and either
        numeric values or mean, median, min, max, p1, p5, p10 p25, p50, p75,
        p90, p95, p99. The default is mean for all variables. The statistics
        p1, p5, ..., p99, are the 1st, 5th, ..., 99th percentile.

    iterate(#) is passed directly to nlcom. It specifies the maximum number
        of iterations used to find the optimal step size in calculating
        numerical derivatives. You should rarely have to use this option.
        See: nlcom.

Examples

    . dirifit propfood, mu(income nchild) phi(haspartner)

    . ddirifit

    . ddirifit, at(income median nchild 2)

Author

    Maarten L. Buis, Vrije Universiteit Amsterdam
    m.buis@fsw.vu.nl


Also see

    Online: help for dirifit and nlcom