[R] cube root of a negative number

[Kjetil Halvorsen]

Look at this:

> x <- as.complex(-4)
> x
[1] -4+0i
> x^(1/3)
[1] 0.793701+1.37473i
> (-4)^(1/3)
[1] NaN

It seems that R gives you the principal root, which is complex, and
not the real root.

Kjetil

On Tue, Oct 26, 2010 at 8:05 PM, Gregory Ryslik <rsaber at comcast.net> wrote:
> Hi,
>
> This might be me missing something painfully obvious but why does the cube root of the following produce an NaN?
>
>> (-4)^(1/3)
> [1] NaN
>>
>
> As we can see:
>
>> (-1.587401)^3
> [1] -4
>
> Thanks!
>
> Greg
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