sampleSelection: model.matrix.selection – R documentation

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sampleSelection

model.matrix.selection

Design Matrix of Selection Models

Description

Create design matrix of sample selection models

Usage

## S3 method for class 'selection'
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 treatment model) 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.

Author(s)

Arne Henningsen