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87 lines
3.4 KiB
Plaintext
87 lines
3.4 KiB
Plaintext
7 months ago
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help for ^countfit^ - 03Nov2005
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Compare fit of alternive count models
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-------------------------------------
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^countfit^ varlist [if] [in]^,^ [^inf^late^(^varlist2^)^ ^noc^onstant ^p^rm ^n^breg
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^zip^ ^zin^b ^g^enerate^(^prefix^)^ ^replace^ ^note(^string^)^
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^graph^export^(^filename[^, replace^]^)^ ^nog^raph ^nod^ifferences ^noprt^able
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^noe^stimates ^nof^it ^nodash^ ^max^count(#) ^noi^sily]
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Description
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-----------
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^countfit^ compares the fit of the Poissin, negative binomial, zero-inflated
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Poisson and zero-inflated negative binomial models, generateing a table of
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estimates, a table of differences between observed and average estimated
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probabilities for each count, a graph of these differences, and various tests
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and measures used to compare the fit of count models.
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Specifying the model
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--------------------
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Immediately afer the command name ^countfit^ you specify the dependent and
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independent variables as you would with ^poisson^ or the other models. For
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zero-inflated models, the ^inflate^ option is used in the same was as in the
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^zip^ and ^zinb^ commands. ^noconstant^ can be used to exclude the constant
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term.
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Options to select the models to fit
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-----------------------------------
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By default, ^poisson^, ^nbreg^, ^zip^ and ^zinb^ are estimated. If you
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only want some of these models, specify the modesl you want with:
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^prm^ - include ^poisson^
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^nbreg^ - include ^nbreg^
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^zip^ - include ^poisson^
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^zinb^ - include ^poisson^
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Options to label results
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------------------------
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^generate()^ is up to five letters to name the variables that are created
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and to label the models in the output. This name is placed in front
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of the type of model (e.g., namePRM). This is optional but will help
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keep track of results from multiple specifications of models.
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^replace^ will replace variables created with the ^generate^ option if they
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already exist.
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^note()^ is a label added to the graph that is saved.
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^graphexport()^ contains options to be sent to the ^graph export^ command to
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export the graph that is create. For example, ^graph(mdl.emf, replace)^
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would save the file mdl.emf and replace it if it exists. If this option
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is not included, the graph is not saved.
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Options controlling what is printed
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-----------------------------------
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^noisily^ shows the output from the estimation commands called by ^countfit^.
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^nograph^ suppress graph of differences from observed counts.
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^nodifferences^ suppress table of differences from observed counts.
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^noprtable^ suppresses table of predictions for each model.
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^noestimates^ suppress table of estimated coefficients.
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^nofit^ suppress table of fit statistics and test of fit
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^nodash^ suppress dashed lines between measures of fit
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^maxcount()^ number of counts to evaluate.
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^noisily^ includes output from Stata estimation commands; without this option
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the results are only shown in the ^estimates table^ output.
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Notes
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-----
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^countfit^ is based on the results from the Stata models described above,
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the predictions computed by ^prcounts^, and the fit measures computed by
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^fitstat^.
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Examples
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--------
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^. use couart2^
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^. countfit art fem mar kid5 phd ment, inf(ment fem) nbreg zinb nograph^
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.-
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Author: 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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