On 22 Nov 2013, at 07:53 , Rolf Turner <r.tur...@auckland.ac.nz> wrote:
> On 11/22/13 18:47, William Dunlap wrote:
>>> a <- 2; b <- 3; xyplot(1:10 ~ a*(1:10), sub = c(bquote(a == .(a) ~
>>> b==.(b))))
>>>
>>> the subtitle contains three copies of the "a = 2 b = 3" phrase.
>>> Why does it do that? How do I tell it to give me only one copy?
>> To avoid it don't wrap bquote() with c(). The following does what you asked
>> for:
>> a <- 2; b <- 3; xyplot(1:10 ~ a*(1:10), sub = bquote(a == .(a) ~
>> b==.(b)))
>
> Not for me it doesn't. Without the c() wrapper, I get no subtitle at all.
> Your recipe seems to
> work with base graphics and plot() but not with lattice and xyplot(). Also
> the c() wrapper
> seems to have no impact when used with plot().
>
> Moreover I am mystified by the impact of the c() wrapper when used with
> xyplot().
>
> The result returned by bquote() has class "call". The result returned by
> c(bquote(...)) is a
> list, of length 1, whose sole entry is of class "call" and is, as one might
> expect, equal to the
> result returned by bquote().
>
> But why should passing this length-1 list as the value for "sub" cause a
> triplication of the
> subtitle?
I dunno either, but a hint at the reason would be to look at what happens with
xyplot(0 ~ 1, sub=list(quote(1+1)))
When you do computing on the language, sometimes quote()’ing is not sufficient
protection against evaluation. That’s what expression objects are for.
A solution seems to be
xyplot(0 ~ 1, sub=as.expression(
bquote(pi==.(pi) ~ e==.(exp(1)))
))
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
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