Compute the n-th root of x, returning real results for real components of x. For example:nthroot (-1, 3) ⇒ -1 (-1) ^ (1 / 3) ⇒ 0.50000 - 0.86603i
x must have all real entries. n must be a scalar. If n is an even integer and X has negative entries, an error is produced. See also: realsqrt, sqrt, cbrt.