New behaviour of droplevels in Rdevel

[gavinsimpson]

R Core have altered the behaviour of droplevels(). For some initial discussions see #192. The basic issue is that now droplevels is defined as factor(x, ..., exclude = NULL) and this coupled with changes to factor() when exclude = NULL mean behaviour may have changed. To maintain behaviour of R v3.3 we should use droplevels(x, exclude = NA). This issue exists to track changes to the range of functions in vegan that use droplevels.

Current list of functions known to use droplevels

• centroids.cca
• envfit.default
• factorfit
• betadisper (Fixed in ae67eba, see #192)
• hiersimu.default
• adipart.default
• multipart.default

I'm tracking this on the issue-#193 branch.

[jarioksa]

It seems that droplevels has not been stabilized yet, but discussion continues. Probably we need to wait till droplevels() stabilizes.

[gavinsimpson]

Right; I was in two minds whether to continue this when I saw the R-devel thread. However, the proposed changes don't break anything nor rely on whatever behaviour RCore ultimately settles upon, but they do make explicit the behaviour we want/expect/anticipate and so should be robust to RCore tweaking.

I would suggest we don't push out a 2.4-1 just for this though if we don't continue to generate errors when R-devel version settles down. We can hold off till a future 2.5-0 release if that is preferable?

[jarioksa]

It seems that droplevels() behaves now similarly as earlier, and vegan_2.4-0 passes R CMD check without problems. The change was made in this commit:

r71129 | maechler | 2016-08-22 16:40:07 +0300 (Mon, 22 Aug 2016) | 1 line
Changed paths:
   M /trunk/src/library/base/R/factor.R
   M /trunk/src/library/base/man/droplevels.Rd
   M /trunk/tests/reg-tests-1c.R

droplevels() w/ smarter `exclude` default, now compatible to `[, drop=TRUE`

From that point of view, we need not push a new minor release. However, there are other bug fixes that may call for a minor release like discussed in issue #194.

[gavinsimpson]

Merged into master after merging typo. Closing.