show {methods} | R Documentation |
Display the object, by printing, plotting or whatever suits its
class. This function exists to be specialized by methods. The
default method calls showDefault
.
Formal methods for show
will
usually be invoked for automatic printing (see the details).
show(object)
object |
Any R object |
The methods package overrides the base definition of
print.default
to arrange for automatic printing to honor
methods for the function show
. This does not quite manage to
override old-style printing methods, since the automatic printing in
the evaluator will look first for the old-style method.
If you have a class myClass
and want to define a method for
show
, all will be well unless there is already a function named
print.myClass
. In that case, to get your method dispatched for
automatic printing, it will have to be a method for print
. A
slight cheat is to override the function print.myClass
yourself,
and then call that function also in the method for show
with signature "myClass"
.
show
returns an invisible NULL
.
showMethods
prints all the methods for one or more
functions;
showMlist
prints individual methods lists;
showClass
prints class definitions.
Neither of the latter two normally needs to be called directly.
## following the example shown in the setMethod documentation ... setClass("track", representation(x="numeric", y="numeric")) setClass("trackCurve", representation("track", smooth = "numeric")) t1 <- new("track", x=1:20, y=(1:20)^2) tc1 <- new("trackCurve", t1) setMethod("show", "track", function(object)print(rbind(x = object@x, y=object@y)) ) ## The method will now be used for automatic printing of t1 t1 ## Not run: [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] x 1 2 3 4 5 6 7 8 9 10 11 12 y 1 4 9 16 25 36 49 64 81 100 121 144 [,13] [,14] [,15] [,16] [,17] [,18] [,19] [,20] x 13 14 15 16 17 18 19 20 y 169 196 225 256 289 324 361 400 ## End(Not run) ## and also for tc1, an object of a class that extends "track" tc1 ## Not run: [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] x 1 2 3 4 5 6 7 8 9 10 11 12 y 1 4 9 16 25 36 49 64 81 100 121 144 [,13] [,14] [,15] [,16] [,17] [,18] [,19] [,20] x 13 14 15 16 17 18 19 20 y 169 196 225 256 289 324 361 400 ## End(Not run)