poibin.py 文件源码

def get_pmf_xi(self):
        """Return the values of the variable ``xi``.

        The components ``xi`` make up the probability mass function, i.e.
        :math:`\\xi(k) = pmf(k) = Pr(X = k)`.
        """
        chi = np.empty(self.number_trials + 1, dtype=complex)
        chi[0] = 1
        half_number_trials = int(
            self.number_trials / 2 + self.number_trials % 2)
        # set first half of chis:
        chi[1:half_number_trials + 1] = self.get_chi(
            np.arange(1, half_number_trials + 1))
        # set second half of chis:
        chi[half_number_trials + 1:self.number_trials + 1] = np.conjugate(
            chi[1:self.number_trials - half_number_trials + 1] [::-1])
        chi /= self.number_trials + 1
        xi = np.fft.fft(chi)
        if self.check_xi_are_real(xi):
            xi = xi.real
        else:
            raise TypeError("pmf / xi values have to be real.")
        xi += np.finfo(type(xi[0])).eps
        return xi