show                 package:methods                 R Documentation

Show an Object

Description:

     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).

Usage:

     show(object)

Arguments:

  object: Any R object

Details:

     Objects from an S4 class (a class defined by a call to 'setClass')
     will be displayed automatically is if by a call to 'show'.  S4
     objects that occur as attributes of S3 objects will also be
     displayed in this form; conversely, S3 objects encountered as
     slots in S4 objects will be printed using the S3 convention, as if
     by a call to 'print'.

     Methods defined for 'show' will only be inherited  by simple
     inheritance, since otherwise the method would not receive the
     complete, original object, with misleading results.  See the
     'simpleInheritanceOnly' argument to 'setGeneric' and the
     discussion in 'setIs' for the general concept.

Value:

     'show' returns an invisible 'NULL'.

See Also:

     '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.

Examples:

     ## 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)

