denumerate {MASS} | R Documentation |
loglm
allows dimension numbers to be used in place of names in
the formula. denumerate
modifies such a formula into one that
terms
can process.
denumerate(x)
x |
A formula conforming to the conventions of |
The model fitting function loglm
fits log-linear models to
frequency data using iterative proportional scaling. To specify
the model the user must nominate the margins in the data that
remain fixed under the log-linear model. It is convenient to
allow the user to use dimension numbers, 1, 2, 3, ... for the
first, second, third, ..., margins in a similar way to variable
names. As the model formula has to be parsed by terms
, which
treats 1
in a special way and requires parseable variable names,
these formulae have to be modified by giving genuine names for
these margin, or dimension numbers. denumerate
replaces these
numbers with names of a special form, namely n
is replaced by
.vn
. This allows terms
to parse the formula in the usual way.
A linear model formula like that presented, except that where
dimension numbers, say n
, have been used to specify fixed
margins these are replaced by names of the form .vn
which may
be processed by terms
.
denumerate(~(1+2+3)^3 + a/b)
## which gives ~ (.v1 + .v2 + .v3)^3 + a/b