[Gretl-users] Re: eiggen2(), Re() and Im()

On Fri, 10 Jan 2020, Allin Cottrell wrote: > 3) I'm not so sure about Sven's suggestion that (if I'm understanding him > right) sqrt(M), for M a real matrix with some negative elements, should > return an appropriate complex matrix. It's clearly defensible, but it might > produce surprising/puzzling results in some cases so I think it requires > further discussion. This is what R does: <R> > sqrt(as.matrix(c(1, -2))) [,1] [1,] 1 [2,] NaN </R> and this is what Octave (therefore, I presume, Matlab) does: <octave> >> sqrt([1 -2]) ans = 1.00000 + 0.00000i 0.00000 + 1.41421i </octave> Personally, I'd stick with the R approach.