Convenience Methods for Setting Contrasts
This package provides modified versions of
contr.treatment and
contr.sum. contr.sum
gains an optional base argument, analog to the
one of contr.treatment, furthermore,
the base argument may be the name of a
factor level.
contr returns a function that calls either
contr.treatment, contr.sum, etc.,
according to the value given to its first argument.
The contrasts method for "item" objects
returns a contrast matrix or a function to produce
a contrast matrix for the factor into which
the item would be coerced via as.factor or as.ordered.
This matrix or function can be specified by
using contrasts(x)<-value
contr(type,...) contr.treatment(n, base=1,contrasts=TRUE) contr.sum(n,base=NULL,contrasts=TRUE) ## S4 method for signature 'item' contrasts(x,contrasts=TRUE,...) ## S4 replacement method for signature 'item' contrasts(x,how.many) <- value # These methods are defined implicitely by making 'contrasts' generic. ## S4 method for signature 'ANY' contrasts(x,contrasts=TRUE,...) ## S4 replacement method for signature 'ANY' contrasts(x,how.many) <- value
type |
a character vector, specifying the type of the contrasts.
This argument should have a value such that, if e.g. |
... |
further arguments, passed to |
n |
a number of factor levels or a vector of factor levels names, see e.g. |
base |
a number of a factor level or the names of a factor level,
which specifies the baseline category,
see e.g. |
contrasts |
a logical value, see |
how.many |
the number of contrasts to generate, see |
x |
a factor or an object of class "item" |
value |
a matrix, a function or the name of a function |
contr returns a funtion that calls one of contr.treatment,
contr.sum,....
contr.treatment and contr.sum return contrast matrices.
contrasts(x) returns the "contrasts" attribute of an
object, which may be a function name, a function, a contrast matrix or NULL.
ctr.t <- contr("treatment",base="c")
ctr.t
ctr.s <- contr("sum",base="c")
ctr.h <- contr("helmert")
ctr.t(letters[1:7])
ctr.s(letters[1:7])
ctr.h(letters[1:7])
x <- factor(rep(letters[1:5],3))
contrasts(x)
x <- as.item(x)
contrasts(x)
contrasts(x) <- contr.sum(letters[1:5],base="c")
contrasts(x)
missing.values(x) <- 5
contrasts(x)
contrasts(as.factor(x))
# Obviously setting missing values after specifying
# contrast matrix breaks the contrasts.
# Using the 'contr' function, however, prevents this:
missing.values(x) <- NULL
contrasts(x) <- contr("sum",base="c")
contrasts(x)
missing.values(x) <- 5
contrasts(x)
contrasts(as.factor(x))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.