From greg at warnes.net  Tue Apr 28 21:11:12 2015
From: greg at warnes.net (Gregory Warnes)
Date: Tue, 28 Apr 2015 15:11:12 -0400
Subject: [Rd] Add first() and last() to utils?
Message-ID: <CAKorm_sj04vU-zZCrcL7f2ATworD4MkSuACbP92nPfBvnMC_VQ@mail.gmail.com>

Hi all,

I've been using first() and last() for some time instead of x[1] and
x[length(x)] for vectors, and I gradually added methods for lists,
matrices, and data.frames.

In preparing the next release of the 'gdata' package (2.16.1) I settled on
these definitions, which harness the existing methods for head() and tail():

# Simply call 'first' or 'last' with a different default value for 'n'.
first <- function(x, n=1, ...) head(x, n=n, ...)
last  <- function(x, n=1, ...) tail(x, n=n, ...)


This works nicely, but Brian noted that packages 'data.table' and 'xts'
also provide functions/S3 methods for head() and/or tail().

Would it make sense to add these definitions to package 'utils' to make
them generally available?

-Greg

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[Rd] Add first() and last() to utils?
Gregory Warnes