Usage
tobit2(selection, formula, data = sys.frame(sys.parent()),
method="ml",
start=NULL, print.level=0,
y1=FALSE, z=FALSE, y2=FALSE, x=FALSE, model=FALSE,
...)Arguments
selection
a symbolic formula for the selection equation. The
response must be binary variable where 0 corresponds to invisibility
of the outcome and 1 to visibility.
formula
a symbolic formula for the equation of interest.
data
an optional data frame containing the variables in
the model. By default the variables are
taken from environment(formula), typically the environment from
which the function is called
method
the method of calculation: Maximum Likelihood ("ml") or
Heckman 2-step ("2step")
start
numeric, initial values of the parameters. The order is
as follows: gamma (selection equation), beta (the equation of
interest), sigma, rho (distribution of the error terms) for tobit2;
print.level
information about calculations. 0 -- nothing is
printed, bigger numbers give more information.
print.level is sent further to the maximisation algorithm,
see maxNR. y1, z, y2, x, model
logicals. If TRUE the corresponding
components of the fit (the selection response, the selection model
matrix, the equation response, the equation model matrix and both
model frames) are returned.
...
further arguments to the maximisation algorithm,
see maxNR.