R has many operators to carry out different mathematical and logical operations. Operators in R can mainly be classified into the following categories.
These operators are used to carry out mathematical operations like addition and multiplication. Here is a list of arithmetic operators available in R.
|%%||Modulus (Remainder from division)|
An example run
> x <- 5 > y <- 16 > x+y  21 > x-y  -11 > x*y  80 > y/x  3.2 > y%/%x  3 > y%%x  1 > y^x  1048576
Relational operators are used to compare between values. Here is a list of relational operators available in R.
|<=||Less than or equal to|
|>=||Greater than or equal to|
|!=||Not equal to|
An example run
> x <- 5 > y <- 16 > x<y  TRUE > x>y  FALSE > x<=5  TRUE > y>=20  FALSE > y == 16  TRUE > x != 5  FALSE
Operation on Vectors
The above mentioned operators work on vectors. The variables used above were in fact single element vectors. We can use the function
c() (as in concatenate) to make vectors in R. All operations are carried out in element-wise fashion. Here is an example.
> x <- c(2,8,3) > y <- c(6,4,1) > x+y  8 12 4 > x>y  FALSE TRUE TRUE
When there is a mismatch in length (number of elements) of operand vectors, the elements in shorter one is recycled in a cyclic manner to match the length of the longer one. R will issue a warning if the length of the longer vector is not an integral multiple of the shorter vector.
> x <- c(2,1,8,3) > y <- c(9,4) > x+y # Element of y is recycled to 9,4,9,4  11 5 17 7 > x-1 # Scalar 1 is recycled to 1,1,1,1  1 0 7 2 > x+c(1,2,3)  3 3 11 4 Warning message: In x + c(1, 2, 3) : longer object length is not a multiple of shorter object length
Logical operators are used to carry out Boolean operations like
|&||Element-wise logical AND|
||||Element-wise logical OR|
| perform element-wise operation producing result having length of the longer operand. But
|| examines only the first element of the operands resulting into a single length logical vector. Zero is considered
FALSE and non-zero numbers are taken as
TRUE. An example run.
> x <- c(TRUE,FALSE,0,6) > y <- c(FALSE,TRUE,FALSE,TRUE) > !x  FALSE TRUE TRUE FALSE > x&y  FALSE FALSE FALSE TRUE > x&&y  FALSE > x|y  TRUE TRUE FALSE TRUE > x||y  TRUE
These operators are used to assign values to variables.
|<-, <<-, =||Leftwards assignment|
|->, ->>||Rightwards assignment|
= can be used, almost interchangeably, to assign to variable in the same environment.
<<- is used for assigning to variables in the parent environments (more like global assignments). The rightward assignments, although available are rarely used.
> x <- 5 > x  5 > x = 9 > x  9 > 10 -> x > x  10