R: Internal and Group Methods and Generic Functions

Internal and Group Methods and Generic Functions

Usage

Math.data.frame(x, ...)
Math.factor(x, ...)

Ops.data.frame(e1, e2 = NULL)
Ops.factor(e1, e2)
Ops.ordered(e1, e2)

Summary.data.frame(x, ...)
Summary.factor(x, ...)

.Method
.Generic
.Group
.Class

Description

Many R-internal functions are generic and allow methods to be written for. Group methods in particular are available for the "Math", "Ops", and "Summary" group.

Group Dispatching

There are three groups for which methods can be written, namely the "Math", "Ops" and "Summary" groups.

A function f belonging to one of these groups must be .Internal or .Primitive and will automatically be using <grp>.<class> (ob) when f(<ob>) is called, f belongs to group <grp> and <ob> is of class <class>.

Group "Math":
- abs, sign, sqrt,
  floor, ceiling, trunc,
  round, signif
- exp, log,
  cos, sin, tan,
  acos, asin, atan
  cosh, sinh, tanh,
  acosh, asinh, atanh
- lgamma, gamma, gammaCody,
  digamma, trigamma, tetragamma, pentagamma
- cumsum, cumprod, cummax, cummin
Group "Ops":
- "+", "-", "*", "/", "^", "%%", "%/%"
- "&", "|", "!"
- "==", "!=", "<", "<=", ">=", ">"
Group "Summary":
- all, any
- sum, prod
- min, max

Simple Dispatching

The following builtin functions are generic as well, i.e., you can write methods for them:

[, [[

dimnames<-, dimnames, dim<-, dim

c, unlist, as.vector, is.na, is.nan

References

Appendix A, Classes and Methods of
Chambers and Hastie (1992). Statistical Models in S; Wadsworth & Brooks/Cole.

Examples

methods("Math")
methods("Ops")
methods("Summary")

d.fr <- data.frame(x=1:9, y=rnorm(9))
data.class(1 + d.fr) == "data.frame" ##-- add to d.f. ...

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