Compute the real (non-complex) n-th root of x.
x must have all real entries and n must be a scalar.
If n is an even integer and x has negative entries then
nthroot aborts and issues an error.
nthroot (-1, 3) ⇒ -1 (-1) ^ (1 / 3) ⇒ 0.50000 - 0.86603i
See also: realsqrt, sqrt, cbrt.