sampleSelection (version 1.0-4)

model.matrix.selection: Design Matrix of Selection Models

Description

Create design matrix of sample selection models

Usage

"model.matrix"(object, part = "outcome", ... )

Arguments

object

object of class selection.

part

character string indication which design matrix/matrices to extract: "outcome" for the design matrix/matrices of the outcome equation(s) or "selection" for the design matrix of the selection equation.

...

further arguments passed to other methods (e.g. model.matrix.binaryChoice or model.matrix).

Value

If argument part is "selection", the design matrix of the selection equation is returned.If argument part is "outcome", the design matrix of the outcome equation (tobit-2) or a list of two outcome matrices (tobit-5 model) is returned. All unobserved outcomes, including the corresponding explanatory variables are set to NA, even in case where valid values were supplied for estimation.

See Also

model.matrix, selection, model.frame.selection, and selection-methods.