| attr | R Documentation |
Get or set specific attributes of an object.
attr(x, which, exact = FALSE)attr(x, which) <- value
x | an object whose attributes are to be accessed. |
which | a non-empty character string specifying which attributeis to be accessed. |
exact | logical: should |
value | an object, the new value of the attribute, or |
These functions provide access to a single attribute of an object.The replacement form causes the named attribute to take the valuespecified (or create a new attribute with the value given).
The extraction function first looks for an exact match towhichamongst the attributes ofx, then (unlessexact = TRUE)a unique partial match.(Settingoptions(warnPartialMatchAttr = TRUE) causespartial matches to give warnings.)
The replacement function only uses exact matches.
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.)
The extractor function allows (and does not match) empty and missingvalues ofwhich: the replacement function does not.
NULL objects cannot have attributes and attempting toassign one byattr gives an error.
Both are primitive functions.
For the extractor, the value of the attribute matched, orNULLif no exact match is found and no or more than one partial match is found.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)The New S Language.Wadsworth & Brooks/Cole.
attributes
# create a 2 by 5 matrixx <- 1:10attr(x,"dim") <- c(2, 5)
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