The COUNTREG Procedure
- Overview
- Getting Started
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Syntax
Functional SummaryPROC COUNTREG StatementBAYES StatementBOUNDS StatementBY StatementCLASS StatementDISPMODEL StatementFREQ StatementINIT StatementMODEL StatementNLOPTIONS StatementOUTPUT StatementPERFORMANCE StatementPRIOR StatementRESTRICT StatementSCORE StatementSHOW StatementSPATIALDISPEFFECTS StatementSPATIALEFFECTS StatementSPATIALID StatementSPATIALZEROEFFECTS StatementSTORE StatementTEST StatementWEIGHT StatementZEROMODEL Statement -
DetailsSpecification of RegressorsMissing ValuesPoisson RegressionConway-Maxwell-Poisson RegressionNegative Binomial RegressionZero-Inflated Count Regression OverviewZero-Inflated Poisson RegressionZero-Inflated Conway-Maxwell-Poisson RegressionZero-Inflated Negative Binomial RegressionSpatial Lag of X ModelVariable SelectionPanel Data AnalysisBY Groups and Scoring with an Item StoreParameter Naming Conventions for the RESTRICT, TEST, BOUNDS, and INIT StatementsComputational ResourcesNonlinear Optimization OptionsCovariance Matrix TypesDisplayed OutputBayesian AnalysisPrior DistributionsAutomated MCMC AlgorithmMarginal LikelihoodOUTPUT OUT= Data SetOUTEST= Data SetODS Table NamesODS Graphics
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Examples
- References
ZEROMODEL Statement
-
ZEROMODEL dependent variable
<zero-inflated regressors> </options>;
The ZEROMODEL statement is required if you specify either ZIP or ZINB in the DIST= option in the MODEL statement. If ZIP or ZINB is specified, then the ZEROMODEL statement must follow immediately after the MODEL statement. The dependent variable in the ZEROMODEL statement must be the same as the dependent variable in the MODEL statement.
The zero-inflated (ZI) regressors appear in the equation that determines the probability (
) of a zero count. Each of these q variables has a parameter to be estimated in the regression. For example, let 
be the ith observation’s 
vector of values of the q ZI explanatory variables (
is set to 1 for the intercept term). Then is a function of 
, where 
is the 
vector of parameters to be estimated. (The ZI intercept is 
; the coefficients for the q ZI covariates are 
.) If this option is omitted, then only the intercept term is estimated. The “Parameter Estimates” table in the displayed output gives the estimates for the ZI intercept and ZI explanatory
variables; they are labeled with the prefix "Inf_". For example, the ZI intercept is labeled "Inf_intercept". If you specify
Age (a variable in your data set) as a ZI explanatory variable, then the “Parameter Estimates” table labels the corresponding
parameter estimate "Inf_Age".
You can specify the following options after a slash (/):
- LINK=value
-
specifies the distribution function to use to compute probability of zeros. The following distribution functions are supported:
- LOGISTIC
-
specifies the logistic distribution.
- NORMAL
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specifies the standard normal distribution.
If this option is omitted, then the default ZI link function is logistic.
- OFFSET=variable
-
specifies a variable in the input data set to be used as a zero-inflated (ZI) offset variable. The ZI offset variable is included as a term, with its coefficient restricted to 1, in the equation that determines the probability (
) of a zero count. The ZI offset variable cannot be the response variable, the offset variable (if any), or one of the explanatory
variables. The name of the data set variable that is used as the ZI offset variable is displayed in the “Model Fit Summary”
output, where it is labeled as "Inf_offset".
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SELECT=INFO<(option)>
SELECTVAR=INFO<(option)> -
requests that the variable selection method be based on an information criterion. For a list of selection-options, see the section Options for Variable Selection Based on an Information Criterion. For more information about this type of variable selection, see the section Variable Selection Using an Information Criterion.