BUG: polyroot() (PR#751)
Peter I noticed with the original problem that there was a difference between R 1.1.1 and the R 1.2 snapshot from a few weeks ago. I would guess you are not running 1.2 since you get
polyeval(1:5,polyroot(1:5))
[1] -2.220446e-16-2.664833e-16i -2.220446e-16-1.554475e-16i [3] -2.220446e-16+1.436839e-16i -2.220446e-16-5.076235e-16i
and with my snapshot I get
polyeval(1:5,polyroot(1:5))
[1] 3.330669e-16+5.828671e-16i 3.330669e-16+2.220446e-16i [3] -2.220446e-16-3.885781e-16i 3.330669e-16-5.828671e-16i I expect you probably know more about the change than I do, but though I would warn you anyway. Polynomial root solutions can be notoriously ill conditioned, but the problem in the bug report does not seem too bad. (At least the answer does not change much with small coefficient perturbations.) One of the things I noticed in the bug report problem was that polyroot did not seem to be giving complex conjugate pairs. (Although, perhaps I did not look closely enough.) In your example it is not too bad but does starts to show up: print(polyroot(11:1), digits=12) [1] 0.953246161338+0.725110449959i -0.884658051302+0.959966734829i [3] -0.884658773085-0.959966532398i 0.953246339786-0.725110604788i [5] 0.442765752789+1.173740513854i -1.264630746148+0.357262003979i [7] -0.246722911623-1.262885538489i 0.442765716343-1.173740954848i [9] -0.246722399601+1.262885188965i -1.264631088498-0.357261261065i
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