Fit an outcome regression (Q-function) model for a single stage

Fits a single Q-function model at one stage of the SMART. Predictions are obtained both for the unmodified data and for data where the treatment is set to the recommended regime.

Usage

qstep(qmodel, data, response, newdata, regime, txName)

Arguments

qmodel

A modelObj object specifying the outcome regression model.

data

A data frame of individuals used to fit the model (typically those who have completed the stage).

response

A numeric vector or single-column data frame of responses (pseudo-outcomes from later stages or observed outcomes).

newdata

A data frame of individuals for whom predictions are desired (typically those who have reached the stage).

regime

A vector of recommended treatment assignments under the regime being evaluated.

txName

A character string specifying the name of the treatment column to modify (e.g., "a1", "a2").

Value

A list with the following components:

hats_mod

A numeric vector of predicted values under the regime-consistent treatment.

hats_unmod

A numeric vector of predicted values under the actual (unmodified) treatment.

qfit

The fitted modelObj object.