def moffat(self, x, p):
        """Moffat fitting function in 1D.
        p[0]==mean, p[1]==corewidth(gamma), p[2]=power(alpha), p[3]=maxv
        """
        y = (1.0 + (x - p[0]) ** 2 / p[1] ** 2) ** (-1.0 * p[2]) * p[3]
        return y