Returns a vector, matrix, or list as the result of applying a function
to a list.
USAGE:
sapply(X, FUN, ..., simplify=T)
REQUIRED ARGUMENTS:
X:
any S-PLUS object; usually a list.
Missing values (NAs) are allowed if FUN accepts them.
FUN:
function or character string giving the name of a function.
OPTIONAL ARGUMENTS:
...:
other arguments to FUN, if any.
simplify=:
logical flag: if TRUE, the result is simplified, if possible.
VALUE:
object whose first value(s) is (are) the result of FUN
applied to the first component of X, and so on.
If all the
results are the same length and simplify is TRUE,
sapply returns a matrix with one column for each component;
if all the results are scalars, a vector is returned.
Otherwise a list of the results is returned.
DETAILS:
lapply calls a function for each element of a list
and always returns a list.
Function apply can be used to perform similar operations
on sections of a matrix or array, and tapply operates on
data classified by categorical variables.
BUGS:
When FUN is a generic function, f, that calls .Internal instead
of UseMethod (e.g., dim, +, or as.vector) sapply will not find the
correct method for it (it will use the default method).
In those cases it is best to replace FUN=f by FUN=function(x,...)f(x,...).
For example, replace FUN="+" by FUN=function(e1,e2)e1+e2 and
replace FUN=dim by FUN=function(x)dim(x).
This applies to any function that takes another function as an argument,
not just to sapply.