@staticmethod
def nargmin(arr, n):
    """Get the index of the Nth min value in arr.

        Parameters
        ----------
        arr : np.ndarray
            1D array.
        n : int
            If n is 0, this returns the location of the min value in arr.
            If n is 1, this returns the location of the 2nd min value in arr.

        Returns
        -------
        i : int
            Location of the Nth min value in arr.
        """
    return arr.argsort()[:n + 1][-1]
