model.matrix.selection function

Design Matrix of Selection Models

Create design matrix of sample selection models

## 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).

Returns

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

See Also

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