def phi_n(self,n,x):
        """
        constructs the 1-dim basis function (formula (1) in Refregier et al. 2001)

        :param n: The n'the basis function.
        :type name: int.
        :param x: 1-dim position (dimensionless)
        :type state: float or numpy array.
        :returns:  array-- phi_n(x).
        :raises: AttributeError, KeyError
        """
        prefactor = 1./np.sqrt(2**n*np.sqrt(np.pi)*math.factorial(n))
        return prefactor*self.H_n(n,x)*np.exp(-x**2/2.)
constructs the 1-dim basis function (formula (1) in Refregier et al. 2001)

        :param n: The n'the basis function.
        :type name: int.
        :param x: 1-dim position (dimensionless)
        :type state: float or numpy array.
        :returns:  array-- phi_n(x).
        :raises: AttributeError, KeyError