

   AAppppllyy aa FFuunnccttiioonn OOvveerr aa LLiisstt

        lapply(X, FUN, ...)
        sapply(X, FUN, ..., simplify = TRUE)

   AArrgguummeennttss::

          X: list (or vector for `sapply') to be used.

        FUN: the function to be applied.  In the case of func-
             tions like `+', `%*%', etc., the function name
             must be quoted.

        ...: optional arguments to `FUN'.

   simplify: logical; should the result be simplified to a vec-
             tor if possible?

   DDeessccrriippttiioonn::

        `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'
        also accepting vectors as `X', and returning a vector
        or array with `dimnames' if appropriate.

   SSeeee AAllssoo::

        `apply', `tapply'.

   EExxaammpplleess::

        x <- list(a = 1:10, beta = exp(-3:3), logic = c(T,F,F,T))
        # 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)
        sapply(sapply(3:9, seq), fivenum)

