Message-ID: <Pine.GSO.4.44.0203192128260.24417-100000@auk.stats>
Date: 2002-03-19T21:31:35Z
From: Brian Ripley
Subject: should lapply preserve attributes?
In-Reply-To: <1016572547.29959.23.camel@keittlab-6>
On 19 Mar 2002, Timothy H. Keitt wrote:
> I have an application where I need to preserve object attributes across
> calls to 'lapply'. The current definition is:
>
> lapply <- function (X, FUN, ...)
> {
> FUN <- match.fun(FUN)
> if (!is.list(X))
> X <- as.list(X)
> rval <- .Internal(lapply(X, FUN))
> names(rval) <- names(X)
> return(rval)
> }
>
> Would it make sense to replace
>
> names(rval) <- names(X)
>
> with
>
> attributes(rval) <- attributes(X)
>
> ?? I can, of course, make a local function for this, but wondered if
> this change would be useful in general.
No, it would be positively harmful. X might be a data frame, or a time
series .., but rval is only guaranteed to be the same length as X. If you
know more, adjust the object returned by lapply.
--
Brian D. Ripley, ripley@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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