| lapply {base} | R Documentation |
lapply returns a list of the same length as X, each
element of which is the result of applying FUN to the
corresponding element of X.
sapply is a “user-friendly” version of lapply
by default returning a vector or matrix if appropriate.
replicate is a wrapper for the common use of sapply for
repeated evaluation of an expression (which will usually involve
random number generation).
lapply(X, FUN, ...) sapply(X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE) replicate(n, expr, simplify = TRUE)
X |
a vector (atomic or list) or an expressions vector. Other
objects (including classed objects) will be coerced by
as.list. |
FUN |
the function to be applied to each element of X:
see Details. In the case of functions like +, %*%, etc.,
the function name must be backquoted or quoted. |
... |
optional arguments to FUN. |
simplify |
logical; should the result be simplified to a vector or matrix if possible? |
USE.NAMES |
logical; if TRUE and if X is character,
use X as names for the result unless it had names
already. |
n |
number of replications. |
expr |
expression (language object, usually a call) to evaluate repeatedly. |
FUN is found by a call to match.fun and typically
is specified as a function or a symbol (e.g. a backquoted name) or a
character string specifying a function to be searched for from the
environment of the call to lapply.
Function FUN must be able to accept as input any of the
elements of X. If the latter is an atomic vector, FUN
will always be passed a length-one vector of the same type as X.
Simplification in sapply is only attempted if X has
length greater than zero and if the return values from all elements
of X are all of the same (positive) length. If the common
length is one the result is a vector, and if greater than one is a
matrix with a column corresponding to each element of X.
The mode of the simplified answer is chosen to accommodate the modes of
all the values returned by the calls to FUN: see unlist.
if X has length 0, the return value of sapply is always
a 0-length list.
sapply(*, simplify = FALSE, USE.NAMES = FALSE) is
equivalent to lapply(*).
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
apply, tapply,
mapply for applying a function to multiple
arguments, and rapply for a recursive version of
lapply(), eapply for applying a function to each
entry in an environment.
x <- list(a = 1:10, beta = exp(-3:3), logic = c(TRUE,FALSE,FALSE,TRUE)) # compute the list mean for each list element lapply(x,mean) # median and quartiles for each list element lapply(x, quantile, probs = 1:3/4) sapply(x, quantile) i39 <- sapply(3:9, seq) # list of vectors sapply(i39, fivenum) hist(replicate(100, mean(rexp(10))))