Logic {base}R Documentation

Logical Operators

Description

These operators act on logical vectors.

Usage

! x
x & y
x && y
x | y
x || y
xor(x, y)
isTRUE(x)

Arguments

x, y logical vectors, or objects which can be coerced to such or for which methods have been written.

Details

! indicates logical negation (NOT).

& and && indicate logical AND and | and || indicate logical OR. The shorter form performs elementwise comparisons in much the same way as arithmetic operators. The longer form evaluates left to right examining only the first element of each vector. Evaluation proceeds only until the result is determined. The longer form is appropriate for programming control-flow and typically preferred in if clauses.

xor indicates elementwise exclusive OR.

isTRUE(x) is an abbreviation of identical(TRUE,x).

Numeric and complex vectors will be coerced to logical values, with zero being false and all non-zero values being true. Raw vectors are handled without any coercion for !, & and |, with these operators being applied bitwise (so ! is the 1-complement).

The operators !, & and | are generic functions: methods can be written for them individually or via the Ops) group generic function.

NA is a valid logical object. Where a component of x or y is NA, the result will be NA if the outcome is ambiguous. In other words NA & TRUE evaluates to NA, but NA & FALSE evaluates to FALSE. See the examples below.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

See Also

TRUE or logical.

any and all for OR and AND on many scalar arguments.

Syntax for operator precedence.

Examples

y <- 1 + (x <- rpois(50, lambda=1.5) / 4 - 1)
x[(x > 0) & (x < 1)]    # all x values between 0 and 1
if (any(x == 0) || any(y == 0)) "zero encountered"

## construct truth tables :

x <- c(NA, FALSE, TRUE)
names(x) <- as.character(x)
outer(x, x, "&")## AND table
outer(x, x, "|")## OR  table

[Package base version 2.1.0 Index]