logitform {mlogit} | R Documentation |
Two kinds of variables are used in logit models: alternative specific and
individual specific variables. logitform
provides a relevant
class to deal with this specificity and suitable methods to extract
the elements of the model.
logitform(object) ## S3 method for class 'formula': logitform(object) ## S3 method for class 'list': logitform(object) is.logitform(object) ## S3 method for class 'logitform': model.matrix(object, data, ...) ## S3 method for class 'logitform': model.frame(formula, data, ...) ## S3 method for class 'logitform': terms(x, ...) ## S3 method for class 'logitform': update(object,new, ...)
object, x |
for the logitform function, a formula or a list,
for the update and model.matrix methods, a
logitform object, |
new |
the new formula for the update method, |
formula |
a logitform object, |
data |
a data.frame , |
... |
further arguments. |
a logitform
is a formula for which the right hand side may
contain two parts: the first one contains the alternative specific
variables and the second one the individual specific variables. The two
parts are separeted by a ``|
'' sign. If a standard formula is writen, it
is assumed that there are no individual specific variables. Specific
methods are provided to build correctly the model matrix and to update
the formula. The logitform
function is not intended to be use
directly. While using the mlogit
function, the first
argument is automaticaly coerced to a logitform
object.
an object of class logitform
.
Yves Croissant
v <-logitform(y~x1+x2|z1+z2) update(v,.~.+x3-x1|.+z3-z1) update(v,.~.-x1-x2|.) update(v,.~.|.-z1-z2) v <-logitform(y~x1+x2) update(v,.~.-x1+x3) update(v,.~.|z1+z2) data("Fishing",package="Ecdat") colnames(Fishing)[4:11] <- c("pr.beach","pr.pier","pr.boat","pr.charter", "ca.beach","ca.pier","ca.boat","ca.charter") Fish <- mlogit.data(Fishing,varying=c(4:11),shape="wide",choice="mode") f <- logitform(mode~pr+ca|income) X <- model.matrix(f,data=Fish) X[1:6,]