>>>>> Martin Maechler >>>>> on Thu, 28 Sep 2023 12:11:27 +0200 writes:
>>>>> Gregory R Warnes >>>>> on Sat, 23 Sep 2023 13:22:35 -0400 writes: > > It sounds like we need to add arguments (with sensible > > defaults) to complex(), Re(), Im(), is.na.complex() etc to > > allow the user to specify the desired behavior. > > I don't think I'd like such extra flexibility for all these, > ... ;-) and even much less I'd like to be part of the group who > then has to *maintain* such behavior ;-) > [..........] > Currently, I'm actually tending to *simplify* things > drastically, also because it means less surprises in the long > term and much less code reading / debugging in formatting / > printing and dealing with complex numbers. > NB: there *is* the re-opened PR#16752, > https://bugs.r-project.org/show_bug.cgi?id=16752 > where the investigation of the (C-level) R source is a major reason > for my current thinking .. > > What if we decided to really treat complex numbers much more > than currently as pairs of real (i.e. "double") numbers, > notably also when print()ing them? > Consequently, Re() and Im() would continue to return what they > do now (contrary to Hervé's original proposal) also in case of > non-finite numbers. > > Of course, *no* change in arithmetic or other Ops (such as '==') > nor is.na(), is.finite(), is.nan(), etc. > > The current formatting and printing of complex numbers is > complicated in some cases unnecessarily inaccurate and in other > cases unnecessarily *ugly*. > I believe that formatting, we should change to basically format > the (vector of) real parts and imaginary parts separately. > E.g., it is really unnecessarily ugly to switch to exponential > format for both Re and Im, in a situation like this: > > > (-1):2 + 1i*1e99 > [1] 0e+00+1e+99i 0e+00+1e+99i 0e+00+1e+99i 0e+00+1e+99i > > It is very ugly to use exponential/scientific format for the Re() > even if we'd fix the confusing and inaccurate *joint* rounding > of Re and Im. and then, I end with > ... and indeed (as discusses here previously: > While it makes some sense to print NA > identically for logical, integer and double, > it seems often confusing *not* to show <Re> + <Im>i > in the complex case; where that *does* happen for > Inf and NaN: > > > complex(, NA, ((-1):2)) > [1] NA NA NA NA > > complex(, NaN, ((-1):2)) > [1] NaN-1i NaN+0i NaN+1i NaN+2i > > complex(, c(-Inf,Inf), ((-1):2)) > [1] -Inf-1i Inf+0i -Inf+1i Inf+2i > > > > where the first of these *does* keep the finite imaginary > values, but does not show them > > > (cN <- complex(, NA, ((-1):2))); rbind(Re(cN), Im(cN)) > [1] NA NA NA NA > [,1] [,2] [,3] [,4] > [1,] NA NA NA NA > [2,] -1 0 1 2 > > where really, I think we should keep that behavior (*), at least for now: Changing it as well *does* have a relatively large impact, is not back-compatible with (the long history of) S and R, *and* it complicates documentation and teaching unnecessarily. Experts will now how to differentiate the different complex NAs, e.g. by using a simple utilities such as {"format complex", "print complex"} fc <- function(z) paste0("(",Re(z), ",", Im(z),")") pc <- function(z) noquote(fc(z)) which I've used now for testing/"visualizing" different scenarios Martin --- *) simply printing 'NA' in cases where is.na(.) is true and is.nan(.) is false ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
