| Name | operators |
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|---|---|---|---|
| Description |
The unary and binary arithmetic operators are generic functions: methods can be written for them individually or via the Ops group generic function. (See Ops for how dispatch is computed.) If applied to arrays the result will be an array if this is sensible (for example it will not if the recycling rule has been invoked). Logical vectors will be coerced to integer or numeric vectors, FALSE having value zero and TRUE having value one. 1 ^ y and y ^ 0 are 1, always. x ^ y should also give the proper limit result when either (numeric) argument is infinite (one of Inf or -Inf). Objects such as arrays or time-series can be operated on this way provided they are conformable. For double arguments, %% can be subject to catastrophic loss of accuracy if x is much larger than y, and a warning is given if this is detected. %% and x %/% y can be used for non-integer y, e.g. 1 %/% 0.2, but the results are subject to representation error and so may be platform-dependent. Because the IEC 60059 representation of 0.2 is a binary fraction slightly larger than 0.2, the answer to 1 %/% 0.2 should be 4 but most platforms give 5. Users are sometimes surprised by the value returned, for example why (-8)^(1/3) is NaN. For double inputs, R makes use of IEC 60559 arithmetic on all platforms, together with the C system function pow for the ^ operator. The relevant standards define the result in many corner cases. In particular, the result in the example above is mandated by the C99 standard. On many Unix-alike systems the command man pow gives details of the values in a large number of corner cases. Arithmetic on type double in R is supposed to be done in ‘round to nearest, ties to even’ mode, but this does depend on the compiler and FPU being set up correctly. |
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| Syntax | + x - x x + y x - y x * y x / y x ^ y x %% y x %/% y | ||
| Parameters |
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