From tplate at blackmesacapital.com  Fri Jul 23 16:45:59 2004
From: tplate at blackmesacapital.com (Tony Plate)
Date: Fri Jul 23 16:46:11 2004
Subject: [Rd] all.equal(, ) not considering names [was "vector
	documentation error?"]
In-Reply-To: <16638.34549.228605.464549@gargle.gargle.HOWL>
References: <40FE65C5.1070708@pdf.com>
	<16638.34549.228605.464549@gargle.gargle.HOWL>
Message-ID: <6.1.0.6.2.20040721112303.0446d180@mailhost.blackmesacapital.com>

At Wednesday 09:08 AM 7/21/2004, Martin Maechler wrote:
> >>>>> "Spencer" == Spencer Graves <spencer.graves@pdf.com>
> >>>>>     on Wed, 21 Jul 2004 05:47:01 -0700 writes:
>
>     Spencer> The help file for "vector" in R 1.9.1 for Windows includes the
>     Spencer> following:
>
>     Spencer> x <- c(a = 1, b = 2)
>     Spencer> is.vector(x)
>     Spencer> as.vector(x)
>     Spencer> all.equal(x, as.vector(x)) ## FALSE
>
>     Spencer> I ran this just now and got TRUE.
>
>yes, I get this as well {R-patched on Linux}.
>
>I'm sure that it never returned FALSE, since  all.equal()
>doesn't ever.   However it *did* give non TRUE
>in R versions up to 1.6.2 :
>
>   > x <- c(a=1,b=2); all.equal(x, as.vector(x))
>   [1] "names for target but not for current" "TRUE"
>
>and it does give something similar in the our S-plus 6.1 version.
>
>Our documentation does nowhere specify what should happen
>exactly in this case, but I do doubt that the current behavior
>is correct.
>What do other (long time S language) users think?

Sometimes I want one thing, sometime the other.  What I generally do when I 
need a test for equivalence is construct one, by trial and error, that 
works for the situation at hand, since the documentation for these types of 
things in various implementations of the S-language tends to be not 
comprehensive.  So, above all, I don't want the behavior to change.

The current behavior in R seems to vaguely follow the spirit of the 
documentation for all.equal, which emphasizes approximation in numeric 
comparisons, and ignores the issues of names (which is just what the 
current implementation of the function does too).  It might be nice to have 
an argument ignore.names that is passed down recursively, but that would 
probably be difficult to add since all.equal is a generic function.

I'd argue for the documentation being updated to reflect the current 
behavior (i.e., ignore names).

-- Tony Plate


[Rd] all.equal(, ) not considering names [was "vector documentation error?"]
Tony Plate