[R-pkg-devel] test script output

[Kevin R. Coombes]

Thanks for the quick (detailed) response.

On 1/31/2025 12:23 PM, Martin Maechler wrote:
>>>>>> Kevin R Coombes
>>>>>>      on Fri, 31 Jan 2025 11:48:33 -0500 writes:
>      > Hi,
>
>      > I have a package that has been in CRAN for years and is now failing
>      > checks because some of the output of a test script is differing on some
>      > machines in the fifth or sixth decimal place. I have managed to fix most
>      > of these issues (by using the "digits" argument in calls to "summary" to
>      > hide the differences). the only one that remains yields this R CMD check
>      > report:
>
>      > Comparing ‘testDiff.Rout’ to ‘testDiff.Rout.save’ ...52c52
>      > < 2.600e-06 1.328e-01 4.666e-01 1.060e+00 1.369e+00 1.091e+01
>      > ---
>      > > 0.000003  0.132800  0.466600  1.060000  1.369000 10.910000
>
>      > Here the digit-limited output is the same (to a human mathematician, though not to a string-matching computer), but one machine has decided to report the output in scientific notation.
>
> I'm guessing you are slightly off here:
> Almost surely it's *not* a difference in machine/platform but only in versions
> of R-devel.
The original issues *were* platform dependent, where the fifth digit was 
off-by-one on some platforms. You are correct that what is left is 
because of your change in R-devel.
>
> My guess comes from the fact that I've been the R core member
> who committed this change to R-devel :
>    ------------------------------------------------------------------------
>    r87625 | maechler | 2025-01-24 16:58:25 +0100 (Fri, 24 Jan 2025)
>
>    parametrize & improve accuracy in print(summary(<numbers>))
>    ------------------------------------------------------------------------
>
> a week ago.
> ... and BTW, if you look carefully, for the first entry, the new
> output *is* slightly more accurate also in your example.
Certainly, it is more accurate. But less accurate (in the form of fewer 
digits) was what I needed to solve the cross-platform issues in the 
current release.
> I agree that the switch from fixed point to
> exponential/scientific format is "unlucky" in this case
> [and even unnecessary: in this case, keeping fixed format and
>   showing one digit more (using the same amount of characters),
>   one could also have shown the 0.0000026 ...]
>
> A workaround for you may be to set something like
>
>     options(scipen = 2) # default is 0
>
> in your testDiff.R  script  before printing
>
> All this is only in R-devel, the development version of R...
> and I have contemplated to add more tweaks to
> print.summaryDefault()  for that upcoming version of R.
>
> The fear stopping me to do more tweaking was that the
> consequence could be even *more* (still small) changes in such
> summary() printing output.
>
>      >  Both versions were produced by a command equivalent to
>      > print(summary(x, digits = 4))
>
> As you may (or may not ..;-) guess from the above commit message ("parametrize")
> is that  print(summary(<numbers>)) got a new argument zdigits.
Yes. But I can't use the new devel-version argument to fix the problem 
in the current release...
> So, instead of     print(summary(x, digits = 4))
> you can, from R version 4.5 (currently only in the development
> version of R) on use
>
>      print(summary(x, digits = 4), digits = .., zdigits = ..)
>
> but you could also --- already in current versions of R ---
> tweak the output using
>
>      print(summary(x, digits = 4), digits = <n>)
>
> where you can play to see if  n=3 , n=4, or n=5
> help you getting better results ..
> ... actually *not* 'digits = 4'  for summary() at all,
> but only the digits argument to print(.)   {where you'll get a
> the new 'zdigits' argument *additionally* in R-devel and future
> R version's}.
>
>
>      > What is the best cross-platform way to ensure that the output gets printed in the same format? Set "options(scipen=999)"?
>
> That's clearly too extreme to generally,
> (I mentioned `scipen = 2` earlier).
>
>> Alternatively, pass some argument to "print" as well as to  "summary"?
> yes, see above.
>
>> (The other alternative I am considering is to just delete the script from the "tests" directory.)
> (I don't think that would be a good idea, .. but rather a very b.. one)

Ah, but it may have helped someone who knew what they were talking about 
to answer more rapidly to avoid the bad solution. Thanks again.

I will try the options(scipen) fix for now, and keep the new zdigts 
argument in mind going forward.

>
>
>      > Thanks,
>      > Kevin
> Best,
> Martin
>