scipy.misc.derivative is deprecated

[kandersolar]

scipy v1.10.0 (released Jan 3, 2023) has deprecated scipy.misc.derivative, a function used by pvlib.ivtools.sdm.pvsyst_temperature_coeff. The deprecation notice mentions some alternatives (although I'm not confident a new dependency is warranted in our case):

pvlib/ivtools/sdm.py:1347: DeprecationWarning: scipy.misc.derivative is deprecated in SciPy v1.10.0; and will be completely removed in SciPy v1.12.0. You may consider using findiff: https://github.com/maroba/findiff or numdifftools: https://github.com/pbrod/numdifftools

Noticed in this CI run: https://github.com/pvlib/pvlib-python/actions/runs/3992734328/jobs/6848836375#step:9:130

[cwhanse]

I noticed that too, in other work. scipy is not going to provide any numeric differentiation tools. If we keep the pvsyst_temperature_coeff function (I vote yes), and are considering a new dependency, I vote against either autograd or its successor, JAX; they are awkward since they wrap numpy. My preference would be to code our own calculation using a finite difference formula.

[mikofski]

Maybe check statsmodels I seem to recall that it has a simple derivative function, but I can't find it quickly now so maybe I was mistaken?

[adriesse]

+1 for explicit finite difference calculation. I would go so far as to say such a simple calculation should not have been outsourced to a general-purpose function.