Hi Peter, When using units, if `a` is not angular (or dimensionless), I don't see how one could write code in which your example wouldn't fail... But I may be missing something, since for your example one would just realize that cos(ka)+i sin(ka) = exp(ika), in which case the log is just ika and one can the whole complexity...
All the best, Marten On Fri, Oct 27, 2017 at 3:24 PM, Peter Creasey <p.e.creasey...@googlemail.com> wrote: >> Date: Thu, 26 Oct 2017 17:27:33 -0400 >> From: Marten van Kerkwijk >> >> That sounds somewhat puzzling as units cannot really propagate without >> them somehow telling how they would change! (e.g., the outcome of >> sin(a) is possible only for angular units and then depends on that >> unit). But in any case, the mailing list is probably not the best case >> to discuss this - rather, I look forward to -- and will most happily >> give feedback on -- a NEP or other more detailed explanation! >> > > > So whilst it’s true that trigonometric functions only make sense for > dimensionless quantities, you might still want to compute them for > dimensional quantities for reasons of computational efficiency. Taking > your example of sin(a) in a spectral density identity: > > log(cos(ka) + i sin(ka)) = k log(cos(a) + i sin(a)) > > so if you are computing the LHS for many k and a single a (i.e k the > wavenumber and ka dimensionless) then you might prefer the RHS, which > actually uses sin(a). > > Peter > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@python.org > https://mail.python.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion
