[Rd] cummax / cummin for complex numbers

[Ben Bolker]

Michael Haupt <michael.haupt <at> oracle.com> writes:

> 
> Dear all,
> 
> in R 3.1.0, this is happening:
> 
> > cummin(c(1+1i,2-3i,4+5i))
> Error in cummin(c(1 + (0+1i), 2 - (0+3i), 4 + (0+5i))) : 
>   'cummax' not defined for complex numbers
> > cummax(c(1+1i,2-3i,4+5i))
> Error in cummax(c(1 + (0+1i), 2 - (0+3i), 4 + (0+5i))) : 
>   'cummin' not defined for complex numbers
> 
> It may be fixed in R-devel, but I thought I'd mention it to make sure ...
> 
> Best,
> 
> Michael

  Well, it is documented in the development version:

   x: a numeric or complex (not ‘cummin’ or ‘cummax’) object, or an
          object that can be coerced to one of these.

I imagine the problem is in coming up with a good, consistent definition
of the min/max for complex numbers: would you prefer min/max modulus,
phase, real part, imaginary part ... ? max()/min() aren't even defined
for complex numbers in R ...