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help for ^prvalue^ - 1.7.4 - 10/27/00
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Get predicted values for regression models for a given set of values
for the independent variables.
----------------------------------------------------------------------------

    ^prvalue^[^if^ exp] [^in^ range] [, ^x(^variables_and_values^)^][^r^est^(^stat^)^]
        [^l^evel^(^#^)^][^s^ave][^d^if][^b^rief][all][^max^cnt ^(^#^)^][^noba^se][^nola^bel]
        [^ys^tar]

    where

    ^variables_and_values^ is an alternating list of variables and either
        numeric values or mean, median, min, max, upper, lower, previous

    ^stat^ is either mean, median, min, max, upper, lower, previous, grmean
        (group mean), grmedian, grmin, grmax

Description
-----------

After estimating a regression model, ^prvalue^ computes the predicted values
at specific values of the independent variables.  When appropriate, predicted
probabilities are also provided.

By default, the discrete and marginal change is calculated holding all other
variables at their mean.  Values for specific independent variables can be
set using the x() option after ^prvalue^.  For example, to compute predicted
values when educ is 10 and age is 30, type ^prvalue, x(educ=10 age=30)^.
Values for the unspecified independent variables can be set using the rest()
option, e.g., ^prvalue, x(educ=10 age=30) rest(mean)^.  The ^if^ and ^in^
conditions specify conditions for computation of means, min, etc., that are
used with rest().

The command works with cloglog, cnreg, gologit, intreg, logistic, logit,
mlogit, nbreg, ologit, oprobit, poisson, probit, regress, tobit, zinb, and
zip.

Options
-------

^save^  save current values of indepenent variables and predictions for
    computing changes using the dif option.

^dif^  computes difference between current predictions and those that were
    saved.

^level()^ sets the level of the confidence interval for predicted values
    or probabilities for the commands for which these are provided.

^maxcnt()^ is the maximum count value for which the probability is computed
    in count models. Default is 9.

^x()^ sets the values of independent variables for calculating predicted
    values.  The list must alternate variable names and values.  The values
    may be either numeric values or can be mean, median, min, max, previous,
    upper, or lower.  The latter cannot be used if rest() specifies a group
    summary statistic (e.g., grmean).

^rest()^ sets the independent variables not specified in x() to their ^mean^
    (default), ^minimum^, ^maximum^, ^median^ when calculating predicted values.
    ^grmean^ sets these independent variables to the mean conditional on the
    variables and values specified in x(); ^grmedian^, ^grmax^, and ^grmin^ can
    also be used.  If ^prvalue^ has already been run after the last estimate,
    ^previous^ will set unspecified variables to their prior values.  For
    models other than mlogit, ^upper^ and ^lower^ can be used to set independent
    variables to their minimum or maximum depending on which will yield the
    upper or lower extreme predicted value.

^all^ specifies that any calculations of means, medians, etc., should use
    the entire sample instead of the sample used to estimate the model.

^nolabel^ uses values rather than value labels in output.

^nobase^ suppresses inclusion of the base values of x in the output.

^brief^ prints only limited output.

^ystar^ print the predicted value of ystar for binary and ordinal models.

Examples
--------

To compute the predicted values for an ordered logit in which all independent
variables are held at the mean:

 . ^oprobit warm yr89 male white age ed prst^
 . ^prvalue^

To compute predicted values where all independent variables are held at their
minimum:

 . ^prvalue, rest(minimum)^

To compute values for white females, holding all other variables at their
median.

 . ^prvalue, x(white=1 male=0) rest(median)^

To compute values for white females, holding all other variables at the
median for white females:

 . ^prvalue, x(white=1 male=0) rest(grmedian)^

To compute values at the minimum of education, holding all other variables
to the mean:

 . ^prvalue, x(ed=min)^

To compare the predicted values for males and females:

 . ^prvalue, x(male=0) save^
 :::
 . ^prvalue, x(male=1) dif^

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Authors: J. Scott Long and Jeremy Freese
         www.indiana.edu/~jslsoc/spost.htm
         spostsup@@indiana.edu
         
         
