On 30/10/2019 9:08 a.m., peter dalgaard wrote:
We commit a similar sin in the help pages, e.g.
example(set.seed) ; runif(2)
example(set.seed) ; runif(2)
gives you the same random uniforms both times. (Of course it isn't that much of
an issue, since you would rarely be running examples before any serious
simulations.)
I think it's pretty common in example code, and that's justifiable. But
it could be avoided by using withr::with_seed() or something equivalent.
Duncan Murdoch
You can fairly easily work around that by saving and restoring .Random.seed. I
wonder if that isn't also true of the cases using set.seed() for other reasons?
-pd
On 30 Oct 2019, at 13:46 , Duncan Murdoch <murdoch.dun...@gmail.com> wrote:
On 30/10/2019 3:28 a.m., Marvin Wright wrote:
Hi all,
I recently found several calls of set.seed() in a CRAN package. These calls are in a
plot function, which could lead to unexpected behaviour. See
https://github.com/sammo3182/interplot/issues/33
<https://github.com/sammo3182/interplot/issues/33> for a description of the
problem.
I checked the CRAN repository policies and could not find anything about this.
I would have expected a policy against setting fixed seeds somewhere in a
package. Am I missing something?
set.seed() writes .Random.seed in the user's global environment, which violates
this policy:
- Packages should not modify the global environment (user’s workspace).
However, every call to a random number generator creates or modifies
.Random.seed as well, and most of those are expected and shouldn't be flagged.
And interplot() is documented to do random simulations, so it would be expected
to change the seed: the issue is that given the same inputs it always changes
it to the same thing. I think that would be quite hard for a test to detect.
Should it be a policy with no test? Maybe, because I agree with you that
interplot()'s set.seed(324) is bad practice.
Duncan Murdoch
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