Passing a call as label to text() works differently when the call involves paste() vs paste0()

-----Original Message-----
From: Duncan Murdoch [mailto:murdoch.duncan at gmail.com]
Sent: Monday, 05 September, 2022 15:49
To: Viechtbauer, Wolfgang (NP); R-devel at r-project.org
Subject: Re: [Rd] Passing a call as label to text() works differently when the
call involves paste() vs paste0()

On 05/09/2022 9:36 a.m., Viechtbauer, Wolfgang (NP) wrote:

Hi all,

Maybe a bit of an esoteric observation, but the second one doesn't work

properly:

x <- 2
plot(NA, xlim=c(0,1), ylim=c(0,1))
text(0.5, 0.55, bquote(paste("x =", .(x))))
text(0.5, 0.45, bquote(paste0("x = ", .(x))))

Note that this has nothing to do in particular with bquote(). This is the same

issue:

plot(NA, xlim=c(0,1), ylim=c(0,1))
text(0.5, 0.55, as.call(list(quote(paste), "x =", 2)))
text(0.5, 0.45, as.call(list(quote(paste0), "x = ", 2)))

I had a look at C_text in plot.c, but couldn't figure out why the second one is

treated differently.

You're using plotmath code, which is documented in ?plotmath.

It doesn't execute paste(), it just uses that name for a similar
operation.  There's no operation named paste0(), so that doesn't work.

The paste() operation doesn't add space, so it's more like paste0() in
any case.

Duncan Murdoch