[Rd] "plot.ts" doesn't respect the value of "pch" (+ blocked from Bugzilla signups)

[Gregory Werbin]

I've had a chance to read the source more thoroughly. The chain of 
events is as follows:

1. Local function `plotts()` is defined with argument `cex` that 
defaults to `par("cex")`
2. `...` is passed to `plotts()`. If "cex" is an element in `...`, 
inside `plotts()` the variable `cex` is assigned thereby (overriding the 
default arg). Importantly, this means that the element "cex" is captured 
and _removed_ from `...`. `...` is eventually passed to `plot.window()`.
3.
   - In the univariate case (NCOL(x) == 1): When `lines.default()` is 
called to actually plot the data 
(https://github.com/wch/r-source/blob/trunk/src/library/stats/R/ts.R#L588 
and 
https://github.com/wch/r-source/blob/trunk/src/library/stats/R/ts.R#L597 
for reference), `cex` is not included in the call.
   - In the bivariate case (NCOL(x) > 1): Because "cex" was captured and 
removed from `...`, it is not passed to `plot.default` when it is called 
(https://github.com/wch/r-source/blob/trunk/src/library/stats/R/ts.R#L548).

It turns out that the "eating" is not being done by `...` but by the 
signature of `plotts`.

The documentation currently reads:

> ...: additional graphical arguments, see 'plot', 'plot.default' and 
> 'par'.

This, to me, suggests parity with the 'plot' function in how the 
arguments in '...' are handled. Therefore either the code is wrong or 
the documentation is incomplete and misleading.

I filed this is as a bug because it's undocumented, and inconsistent 
with how other arguments typically passed through `plot.default` are 
handled.

I'll be happy to do the patch myself -- I just need to know which thing 
to patch (the source or the docs).


Greg


On 2016-08-25 03:00, David Winsemius wrote:

>> On Aug 24, 2016, at 5:59 PM, Gregory Werbin 
>> <greg.werbin at libertymail.net> wrote:
>> 
>> I did a search on Bugzilla for "plot.ts" and didn't find anything on 
>> this issue. I tried to sign up for Bugzilla to report it, but my 
>> e-mail address didn't pass your "syntax checking" for a legal e-mail 
>> address.
>> 
>> The bug is easily reproducible on my machine as follows:
>> 
>> ## start
>> 
>> # generate some data
>> y <- arima.sim(list(), 150)
>> 
>> # this will definitely dispatch to a ".ts" method
>> class(y)[1] == 'ts'
>> 
>> # compare and note that `cex = 0.5` has no effect
>> plot(y, type = 'b', pch = 16)
>> plot(y, type = 'b', pch = 16, cex = 0.5)
>> 
>> # it works if `y` is coerced back to a regular vector
>> plot(as.numeric(y), type = 'b', pch = 16, cex = 0.5)
>> 
>> # another way to see the issue
>> plot.ts(y, type = 'b', pch = 16, cex = 0.5)
>> plot.default(y, type = 'b', pch = 16, cex = 0.5)
>> 
>> ## end
>> 
>> Skimming through source code for `plot.ts`, it seems like the `cex` 
>> argument is being "eaten" by a `...` somewhere without being properly 
>> passed to `plot.default`.
> 
> '...' does not "eat" parameters, it passes them on.
> 
> Looking at the very top of the body we see this in the definition of 
> the internal `plotts` function:
> 
> cex = par("cex"), lty = par("lty"), lwd = par("lwd"),
> axes = TRUE, frame.plot = axes, ann = par("ann"), cex.lab = 
> par("cex.lab"),
> col.lab = par("col.lab"), font.lab = par("font.lab"),
> cex.axis = par("cex.axis"), col.axis = par("col.axis"),
> 
> And at the end of the body we se the call to plotts (including the 
> "dots")
> 
> So I would suggest using par-settings.
> 
> par(cex=0.5)
> plot(y, type = 'b', pch = 16)
> 
> (Question seems more appropriate for r-help.)
> 
> --
> David.
> 
>> The output of `R.version` is:
>> platform       x86_64-apple-darwin15.5.0
>> arch           x86_64
>> os             darwin15.5.0
>> system         x86_64, darwin15.5.0
>> status
>> major          3
>> minor          3.1
>> year           2016
>> month          06
>> day            21
>> svn rev        70800
>> language       R
>> version.string R version 3.3.1 (2016-06-21)
>> nickname       Bug in Your Hair
>> 
>> Greg
>> 
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> David Winsemius
> Alameda, CA, USA