| attributes {base} | R Documentation |
Object Attribute Lists
Description
These functions access an object's attributes.The first form below returns the object's attribute list.The replacement forms uses the list on the right-handside of the assignment as the object's attributes (if appropriate).
Usage
attributes(x)attributes(x) <- valuemostattributes(x) <- valueArguments
x | anyR object; for the replacement functions, not a |
value | an appropriate named |
Details
Unlikeattr it is currently not an error to set attributeson aNULL object: it will first be coerced to an emptylist.
Note that some attributes (namelyclass,comment,dim,dimnames,names,row.names andtsp) are treated specially and have restrictions onthe values which can be set. (Note that this is not true oflevels which should be set for factors via thelevels replacement function.)
Attributes are not stored internally as a list and should be thoughtof as a set and not a vector, i.e, theorder of the elements ofattributes() does not matter. This is also reflected byidentical()'s behaviour with the default argumentattrib.as.set = TRUE. Attributes must have unique names (andNA is taken as"NA", not a missing value).
Assigning attributes first removes all attributes, then sets anydim attribute and then the remaining attributes in the ordergiven: this ensures that setting adim attribute always precedesthedimnames attribute.
Themostattributes assignment takes special care for thedim,names anddimnamesattributes, and assigns them only when known to be valid whereas anattributes assignment would give an error if any are not. Itis principally intended for arrays, and should be used with care onclassed objects. For example, it does not check thatrow.names are assigned correctly for data frames.
The names of a pairlist are not stored as attributes, but are reportedas if they were (and can be set by the replacement form ofattributes).
NULL objects cannot have attributes and attempts toassign them will promote the object to an empty list.
Both assignment and replacement forms ofattributes areprimitive functions.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)The New S Language.Wadsworth & Brooks/Cole.
See Also
Examples
x <- cbind(a = 1:3, pi = pi) # simple matrix with dimnamesattributes(x)## strip an object's attributes:attributes(x) <- NULLx # now just a vector of length 6mostattributes(x) <- list(mycomment = "really special", dim = 3:2, dimnames = list(LETTERS[1:3], letters[1:5]), names = paste(1:6))x # dim(), but not {dim}names