R devel - Mar 2020 - Expressions from boxplot() passed to bxp()

Hi,

Is this expected behavior (R-3.6.0)?

dat <- cbind(x = 1:10, y = 10:1)
ylab <- substitute(X[t], list(t = 2))
plot(dat, ylab = ylab) # works (correctly displays ylab)
boxplot(dat, ylab = ylab) # fails
boxplot(dat, ylab = as.expression(ylab)) # works

Thanks & cheers,
M

It's not new anyway. You see the same behaviour with

boxplot(dat, ylab=quote(X[2]))

and it boils down to the use of do.call("bxp", ...) in the internals. 

As a general matter, expression() exists to prevent this sort of confusion,
e.g., in this construction,
> X <- quote(Y+1); bquote(f(.(X)))
f(Y + 1)

is indistinguishable from just entering f(Y+1), so f has no way of detecting
whether or not it is intended to evaluate Y + 1. The same thing is happening
with do.call: call objects are being "spliced into" the generated
call, and if they are not protected with expression, you have the trouble.

I don't know whether it is worth trying to change this. You know the
workaround.

-pd


> On 27 Mar 2020, at 02:55 , Marius Hofert <marius.hofert at
uwaterloo.ca> wrote:
> 
> Hi,
> 
> Is this expected behavior (R-3.6.0)?
> 
> dat <- cbind(x = 1:10, y = 10:1)
> ylab <- substitute(X[t], list(t = 2))
> plot(dat, ylab = ylab) # works (correctly displays ylab)
> boxplot(dat, ylab = ylab) # fails
> boxplot(dat, ylab = as.expression(ylab)) # works
> 
> Thanks & cheers,
> M
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

On Fri, 27 Mar 2020, peter dalgaard wrote:
> It's not new anyway. You see the same behaviour with
>
> boxplot(dat, ylab=quote(X[2]))
>
> and it boils down to the use of do.call("bxp", ...) in the
internals.
>
> As a general matter, expression() exists to prevent this sort of confusion,
e.g., in this construction,
>
>> X <- quote(Y+1); bquote(f(.(X)))
> f(Y + 1)
>
> is indistinguishable from just entering f(Y+1), so f has no way of
detecting whether or not it is intended to evaluate Y + 1. The same thing is
happening with do.call: call objects are being "spliced into" the
generated call, and if they are not protected with expression, you have the
trouble.
do.call has a 'quote' argument that can be used to address this. The
default is quote = FALSE, which means all arguments will be evaluated
by the called function. Which is fine for arguments that evaluate to
themselves. For symbols and calls it isn't.

I did try to make the case some time ago that quote = TRUE should be
the default but I lost that argument.

It might be worth revisiting that, or at least reviewing the uses of
do.call in our code sometime (there are a couple of hundred).

Best,

luke
>
> I don't know whether it is worth trying to change this. You know the
workaround.
>
> -pd
>
>
>
>> On 27 Mar 2020, at 02:55 , Marius Hofert <marius.hofert at
uwaterloo.ca> wrote:
>>
>> Hi,
>>
>> Is this expected behavior (R-3.6.0)?
>>
>> dat <- cbind(x = 1:10, y = 10:1)
>> ylab <- substitute(X[t], list(t = 2))
>> plot(dat, ylab = ylab) # works (correctly displays ylab)
>> boxplot(dat, ylab = ylab) # fails
>> boxplot(dat, ylab = as.expression(ylab)) # works
>>
>> Thanks & cheers,
>> M
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>
>
-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney at uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu