methods (version 3.4.1)

showMethods: Show all the methods for the specified function(s) or class

Description

Show a summary of the methods for one or more generic functions, possibly restricted to those involving specified classes.

Usage

showMethods(f = character(), where = topenv(parent.frame()),
            classes = NULL, includeDefs = FALSE,
            inherited = !includeDefs,
            showEmpty, printTo = stdout(), fdef)
.S4methods(generic.function, class)

Arguments

f

one or more function names. If omitted, all functions will be shown that match the other arguments.

The argument can also be an expression that evaluates to a single generic function, in which case argument fdef is ignored. Providing an expression for the function allows examination of hidden or anonymous functions; see the example for isDiagonal().

where

Where to find the generic function, if not supplied as an argument. When f is missing, or length 0, this also determines which generic functions to examine. If where is supplied, only the generic functions returned by getGenerics(where) are eligible for printing. If where is also missing, all the cached generic functions are considered.

classes

If argument classes is supplied, it is a vector of class names that restricts the displayed results to those methods whose signatures include one or more of those classes.

includeDefs

If includeDefs is TRUE, include the definitions of the individual methods in the printout.

inherited

logical indicating if methods that have been found by inheritance, so far in the session, will be included and marked as inherited. Note that an inherited method will not usually appear until it has been used in this session. See selectMethod if you want to know what method would be dispatched for particular classes of arguments.

showEmpty

logical indicating whether methods with no defined methods matching the other criteria should be shown at all. By default, TRUE if and only if argument f is not missing.

printTo

The connection on which the information will be shown; by default, on standard output.

fdef

Optionally, the generic function definition to use; if missing, one is found, looking in where if that is specified. See also comment in ‘Details’.

generic.function, class

See methods.

Value

If printTo is FALSE, the character vector that would have been printed is returned; otherwise the value is the connection or filename, via invisible.

Details

See methods for a description of .S4methods.

The name and package of the generic are followed by the list of signatures for which methods are currently defined, according to the criteria determined by the various arguments. Note that the package refers to the source of the generic function. Individual methods for that generic can come from other packages as well.

When more than one generic function is involved, either as specified or because f was missing, the functions are found and showMethods is recalled for each, including the generic as the argument fdef. In complicated situations, this can avoid some anomalous results.

References

Chambers, John M. (2008) Software for Data Analysis: Programming with R Springer. (For the R version.)

Chambers, John M. (1998) Programming with Data Springer (For the original S4 version.)

See Also

setMethod, and GenericFunctions for other tools involving methods; selectMethod will show you the method dispatched for a particular function and signature of classes for the arguments.

methods provides method discovery tools for light-weight interactive use.

Examples

require(graphics)

## Assuming the methods for plot
## are set up as in the example of help(setMethod),
## print (without definitions) the methods that involve class "track":
showMethods("plot", classes = "track")

# Function "plot":
# x = ANY, y = track
# x = track, y = missing
# x = track, y = ANY

require("Matrix")
showMethods("%*%")# many!
    methods(class = "Matrix")# nothing
showMethods(class = "Matrix")# everything
showMethods(Matrix:::isDiagonal) # a non-exported generic
<!-- %end{dontrun} -->

<!-- %% An example of showing methods from a loaded, -->
<!-- %% but not attached namespace. -->
if(no4 <- is.na(match("stats4", loadedNamespaces())))
   loadNamespace("stats4")
showMethods(classes = "mle") # -> a method for show()
if(no4) unloadNamespace("stats4")