length

R Base 3.6.2

Get or set the length of vectors (including lists) and factors, and of any other R object for which a method has been defined.

Syntax

length(x)
length(x) &lt;- value

Arguments

Parameter	Description
`x`	an R object. For replacement, a vector or factor.
`value`	a non-negative integer or double (which will be rounded down).

Return Value

The default method for length currently returns a non-negative integer of length 1, except for vectors of more than \(2^{31}-1\) elements, when it returns a double. For vectors (including lists) and factors the length is the number of elements. For an environment it is the number of objects in the environment, and NULL has length 0. For expressions and pairlists (including language objects and dotlists) it is the length of the pairlist chain. All other objects (including functions) have length o

Details

Both functions are generic: you can write methods to handle specific classes of objects, see InternalMethods. length<- has a "factor" method. The replacement form can be used to reset the length of a vector. If a vector is shortened, extra values are discarded and when a vector is lengthened, it is padded out to its new length with NAs (nul for raw vectors). Both are primitive functions.

Examples

Example

# NOT RUN {
length(diag(4))  # = 16 (4 x 4)
length(options())  # 12 or more
length(y ~ x1 + x2 + x3)  # 3
length(expression(x, {y <- x^2; y+2}, x^y))  # 3

## from example(warpbreaks)
require(stats)

fm1 <- lm(breaks ~ wool * tension, data = warpbreaks)
length(fm1$call)      # 3, lm() and two arguments.
length(formula(fm1))  # 3, ~ lhs rhs
# }