【每天一个R语言命令】-methods

【描述】

List all available methods for a S3 and S4 generic function, or all methods for an S3 or S4 class.
关于S3和S4的介绍见https://www.jianshu.com/p/1caf31c2289d

【用法】
methods(generic.function, class)
.S3methods(generic.function, class, envir=parent.frame())

S3 method for class 'MethodsFunction'

format(x, byclass = attr(x, "byclass"), ...)

S3 method for class 'MethodsFunction'

print(x, byclass = attr(x, "byclass"), ...)
【参数】

generic.function
a generic function, or a character string naming a generic function.

class
a symbol or character string naming a class: only used if generic.function is not supplied.

envir
the environment in which to look for the definition of the generic function, when the generic function is passed as a character string.

x
typically the result of methods(..), an R object of S3 class "MethodsFunction", see ‘Value’ below.

byclass
an optional logical allowing to override the "byclass" attribute determining how the result is printed, see ‘Details’.

...
potentially further arguments passed to and from methods; unused currently.
【代码】

> methods(is)
 [1] is.array                is.atomic               is.call                 is.character           
 [5] is.complex              is.data.frame           is.double               is.element             
 [9] is.empty.model          is.environment          is.expression           is.factor              
[13] is.finite               is.function             is.infinite             is.integer             
[17] is.language             is.leaf                 is.list                 is.loaded              
[21] is.logical              is.matrix               is.mts                  is.na                  
[25] is.na.data.frame        is.na.numeric_version   is.na.POSIXlt           is.na<-                
[29] is.na<-.default         is.na<-.factor          is.na<-.numeric_version is.name                
[33] is.nan                  is.null                 is.numeric              is.numeric.Date        
[37] is.numeric.difftime     is.numeric.POSIXt       is.numeric_version      is.object              
[41] is.ordered              is.package_version      is.pairlist             is.primitive           
[45] is.qr                   is.R                    is.raster               is.raw                 
[49] is.recursive            is.relistable           is.single               is.stepfun             
[53] is.symbol               is.table                is.ts                   is.tskernel            
[57] is.unsorted             is.vector              
see '?methods' for accessing help and source code
Warning message:
In .S3methods(generic.function, class, envir) :
  function 'is' appears not to be S3 generic; found functions that look like S3 methods