| length {base} | R Documentation |
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) length(x) <- value
x |
an R object. For replacement, a vector or factor. |
value |
an integer: double values will be coerced to 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).
Both are primitive functions.
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.
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.
Package authors have written methods that return a result of
length other than one (Formula) and that return a vector type
double (Matrix), even with non-integer values
(sets).
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
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)
require(stats)
fm1 <- lm(breaks ~ wool * tension, data = warpbreaks)
length(fm1$call) # 3, lm() and two arguments.
length(formula(fm1)) # 3, ~ lhs rhs