S3-S4-R5 dictionary

S3 and S4 are different beasts. So are French and English, but we still have French-English dictionaries even though there’s always the possibility of getting lost in translation.

Below is a table with ‘translations’ that I’ve found can be useful. I intend to keep updating this as I come across other useful ‘translations’. Suggestions welcome. Being much stronger with S3, I hope S4 people share their constructive advice.

Consider an (either S3 or S4) object called x (for simplicity I assume that if x is S3 then its also a list). I use cls, cls1, cls2, etc. to denote names of classes. I use gnrc, gnrc1, gnrc2, etc. to denote names of generic functions.

EDIT: Now covering the R5 system as well. This system is based on reference classes.

S3	S4	R5	Notes
‘elements’	‘slots’	‘fields’
x$	x@	x$
as.cls(x)	as(x, 'cls')
class(x)	class(x)	x$getRefClass()
names(x)	slotNames(class(x)), getSlots(class(x))	x$getRefClass()$fields() OR ls(x)
gnrc.cls	getMethod('gnrc', 'cls')
methods('gnrc')	showMethods('gnrc')	x$getRefClass()$methods()	Because S4 methods allow for dispatching on multiple arguments, there are some pretty important differences between S3 and S4 here: The S3 version shows the names of all methods; S4 version shows the acceptable classes for each argument of the method.
methods(class = 'cls')	showMethods(classes = 'cls')
class(x) <-	setClass	setRefClass	Because of the differences between the three systems, these are VERY rough translations

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