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111 lines
4.0 KiB
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111 lines
4.0 KiB
Plaintext
10 months ago
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help for ^prdc^ - 25Oct2005
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?? if, in, all and ystar options need to be verified.
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Compute descrete change of a specified amount for list of variables.
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--------------------------------------------------------------------
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^prdc^ [varlist] [^if^ exp] [^in^ range] [, ^x(^variables_and_values^)^
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^r^est^(^stat^)^ ^ys^tar ^b^rief ^all ^max^cnt ^(^#^)^ ^noba^se
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^nola^bel ^f^rom^(^#^)^ ^to(^#^)^ ^c^hange^(^#^)^ ^bin^ary
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^u^nit ^sd^ ^unc^entered <you can also use options for confidence
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intervals used with ^prvalue^.]
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where
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^varlist^ contains the names of variables for which discrete change will
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be computed.
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^variables_and_values^ is an alternating list of variables and either
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numeric values or mean, median, min, max, upper, lower, previous
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^stat^ is either mean, median, min, max, upper, lower, previous, grmean
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(group mean), grmedian, grmin, grmax
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Description
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-----------
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^prdc^ computes discrete changes with confidence intervals for regression
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models for categorical and count variables. Discrete change is the
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difference in the predicted value as one independent variable changes
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values while all others are held constant at specified values. ^prdc^ is
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simply a convenient way to execute a save-dif pair of ^prvalue^ commands.
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By default, the discrete change is computed for a unit increase centered
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around the mean.
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Values for specific independent variables can be set using the x() option
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after ^prdc^. Values for the unspecified independent variables can be
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set using the rest() option. The ^if^ and ^in^ conditions specify conditions
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for computation of means, min, etc., that are used with rest().
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The discrete change is computed by the amounts (more than one can be specified)
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specified with the options. ^prdc^ works with all regression programs that are
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compatable with prvalue.
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Options specifying levels of variables
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--------------------------------------
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^x()^ explicitly sets the values of specified independent variables.
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^rest()^ sets the independent variables not specified in x() to their ^mean^
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(default), ^minimum^, ^maximum^, ^median^ when calculating predicted values.
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^grmean^ sets these independent variables to the mean conditional on the
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variables and values specified in x(). If ^prvalue^ has already been run
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after the last estimate, ^previous^ will set unspecified variables to their
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prior values. For models other than mlogit, ^upper^ and ^lower^ can be used
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to set independent variables to their minimum or maximum depending on
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which will yield the upper or lower extreme predicted value.
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Options specifying the amout of change
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--------------------------------------
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^from()^ specifies the start value of the change.
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^to()^ specifies the start value of the change.
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^binary^ specifies a change from 0 to 1.
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^unit^ specifies a unit change at the values specified with x() and rest().
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^sd^ specifies a standard deviation change at the values specified with x()
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and rest().
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^change()^ specifies the amount of the discrete change at the values
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specified with x() and rest().
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^uncentered^ specifies that the uncentered discrete change rather than the
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centered discrete change is to be computed for unit, sd and change.
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Other Options
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-------------
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^maxcnt()^ is the maximum count value for which the probability is computed
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in count models. Default is 9.
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^ystar^ requests change in predicted y*, rather than probabilities.
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^all^ specifies that any calculations of means, medians, etc., should use
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the entire sample instead of the sample used to estimate the model.
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^nolabel^ uses values rather than value labels in output.
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^nobase^ suppresses inclusion of the base values of x in the output.
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^brief^ prints only limited output.
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^help^ presents guide to interpreting headings of output.
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Examples
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--------
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.-
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Authors: J. Scott Long and Jeremy Freese
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www.indiana.edu/~jslsoc/spost.htm
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spostsup@@indiana.edu
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