| Syntax {base} | R Documentation |
Operator Syntax and Precedence
Description
Outlines R syntax and gives the precedence of operators.
Details
The following unary and binary operators are defined. They are listed in precedence groups, from highest to lowest.
:: ::: | access variables in a namespace |
$ @ | component / slot extraction |
[ [[ | indexing |
^ | exponentiation (right to left) |
- + | unary minus and plus |
: | sequence operator |
%any% |> | special operators (including %% and %/%) |
* / | multiply, divide |
+ - | (binary) add, subtract |
< > <= >= == != | ordering and comparison |
! | negation |
& && | and |
| || | or |
~ | as in formulae |
-> ->> | rightwards assignment |
<- <<- | assignment (right to left) |
= | assignment (right to left) |
? | help (unary and binary) |
Within an expression operators of equal precedence are evaluated
from left to right except where indicated. (Note that = is not
necessarily an operator.)
The binary operators ::, :::, $ and @ require
names or string constants on the right hand side, and the first two
also require them on the left.
The links in the See Also section cover most other aspects of the basic syntax.
Note
There are substantial precedence differences between R and S. In
particular, in S ? has the same precedence as (binary) + -
and & && | || have equal precedence.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
See Also
Arithmetic, Comparison, Control,
Extract, Logic,
NumericConstants, Paren,
Quotes, Reserved.
The ‘R Language Definition’ manual.
Examples
## Logical AND ("&&") has higher precedence than OR ("||"):
TRUE || TRUE && FALSE # is the same as
TRUE || (TRUE && FALSE) # and different from
(TRUE || TRUE) && FALSE
## Special operators have higher precedence than "!" (logical NOT).
## You can use this for %in% :
! 1:10 %in% c(2, 3, 5, 7) # same as !(1:10 %in% c(2, 3, 5, 7))
## but we strongly advise to use the "!( ... )" form in this case!
## '=' has lower precedence than '<-' ... so you should not mix them
## (and '<-' is considered better style anyway):
## Not run: ## Consequently, this gives a ("non-catchable") error
x <- y = 5 #-> Error in (x <- y) = 5 : ....
## End(Not run)