R help - Jul 2024 - Bug? plot.formula does need support plot.first / plot.last param in plot.default

Is the following a bug in your opinion? I think so.

This works as expected:

```
with(mtcars, plot(wt, mpg, plot.first = {
    plot.window(range(wt), range(mpg))
    arrows(3, 15, 4, 30)
}))
```

This does not.

```
plot(mpg ~ wt, data = mtcars, plot.first = {
    plot.window(range(wt), range(mpg))
    arrows(3, 15, 4, 30)
})
```

With error:
```
Error in arrows(3, 15, 4, 30) : plot.new has not been called yet
```

The second example should work.
>From the docs:
?plot.formula
"     For the ?plot? method the formula can be of the form ?~ z + y +
     z?: the variables specified on the right-hand side are collected
     into a data frame, subsetted if specified, and displayed by
     ?plot.data.frame?.
"

?plot.data.frame
"     ...: further arguments to ?stripchart?, ?plot.default? or ?pairs?.
"

And plot.default has both plot.first and plot.last

It seems very arbitrary you can't use these parameters with the plot.formula
method specifically.
> sessionInfo()
R version 4.4.1 (2024-06-14)
Platform: x86_64-suse-linux-gnu
Running under: openSUSE Tumbleweed
[...]

That definitely looks like a bug, but not one that anyone will be eager 
to fix.  It's very old code that tried to be clever, and that's the 
hardest kind of code to fix.

Remember Kernighan's Law:  "Everyone knows that debugging is twice as 
hard as writing a program in the first place. So if you?re as clever as 
you can be when you write it, how will you ever debug it?"

Duncan Murdoch

On 2024-07-05 7:35 a.m., Erez Shomron wrote:
> Is the following a bug in your opinion? I think so.
> 
> This works as expected:
> 
> ```
> with(mtcars, plot(wt, mpg, plot.first = {
>      plot.window(range(wt), range(mpg))
>      arrows(3, 15, 4, 30)
> }))
> ```
> 
> This does not.
> 
> ```
> plot(mpg ~ wt, data = mtcars, plot.first = {
>      plot.window(range(wt), range(mpg))
>      arrows(3, 15, 4, 30)
> })
> ```
> 
> With error:
> ```
> Error in arrows(3, 15, 4, 30) : plot.new has not been called yet
> ```
> 
> The second example should work.
> 
>  From the docs:
> 
> ?plot.formula
> "     For the ?plot? method the formula can be of the form ?~ z + y +
>       z?: the variables specified on the right-hand side are collected
>       into a data frame, subsetted if specified, and displayed by
>       ?plot.data.frame?.
> "
> 
> ?plot.data.frame
> "     ...: further arguments to ?stripchart?, ?plot.default? or
?pairs?.
> "
> 
> And plot.default has both plot.first and plot.last
> 
> It seems very arbitrary you can't use these parameters with the
plot.formula method specifically.
> 
>> sessionInfo()
> R version 4.4.1 (2024-06-14)
> Platform: x86_64-suse-linux-gnu
> Running under: openSUSE Tumbleweed
> [...]
> 
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? Fri, 05 Jul 2024 14:35:40 +0300
"Erez Shomron" <r-mails at erezsh.org> ?????:
> This works as expected:
> with(mtcars, plot(wt, mpg, plot.first = {
>     plot.window(range(wt), range(mpg))
>     arrows(3, 15, 4, 30)
> }))
I think you meant panel.first, not plot.first. At least I cannot find
any mention of plot.first in the R source code. In this example,
plot.first ends up being an argument of an internal call from
plot.default() to plot.window(), which evaluates its ellipsis
arguments. If your plot.first expression returned a non-NULL value, you
would also have received a warning:

plot.window(0:1, 0:1, plot.first = message('hello'))
# hello
plot.window(0:1, 0:1, plot.first = 123)
# Warning message:
# In plot.window(0:1, 0:1, plot.first = 123) :
#   "plot.first" is not a graphical parameter

It is indeed documented that "passing [panel.first] from other ?plot?
methods may well not work since it may be evaluated too early". The
plot.formula method deliberately evaluates the arguments in the
ellipsis, and the workaround suggested in
https://bugs.r-project.org/show_bug.cgi?id=14591 doesn't help because
the expression is then evaluated in an undesired environment (parent
frame, not data).

You are correct that plot.formula tries to evaluate all its remaining
arguments in the context of the data passed to the method. In order for
the lazy evaluation to work, plot.formula would have to (1) know and
skip all such arguments by name on line 6, minding partial matching, (2)
rewrite them into the form evalq(original_argument_expression,
model_frame, parent_frame) so that they would be able to access both
the data and the variables visible in the frame of the caller, and (3)
give these expressions to do.call() in place of the original ones.

(1) sounds especially brittle since plot.formula() may dispatch to
other plot.* methods. Additionally, great care will need to be taken
not to break existing code that calls plot.formula, even if it's
already full of workarounds for plot.formula's behaviour.

-- 
Best regards,
Ivan