length {base}R Documentation

Length of an Object


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


length(x) <- value


x an R object. For replacement, a vector or factor.
value an integer.


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).


The default method currently returns an integer of length 1. Since this may change in the future and may differ for other methods, programmers should not rely on it. (Should the length exceed the maximum representable integer, it is returned as NA.)
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 one: note that for functions this differs from S.
The replacement form removes all the attributes of x except its names.


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

See Also

nchar for counting the number of characters in character vectors.


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

[Package base version 2.5.0 Index]