Compute the adjacent-layer correlations

        Parameters
        ----------
        profile : :class:`site.Profile`
            Input site profile

        Yields
        ------
        corr : :class:`numpy.array`
            Adjacent-layer correlations

def _calc_corr(self, profile):
        """Compute the adjacent-layer correlations

        Parameters
        ----------
        profile : :class:`site.Profile`
            Input site profile

        Yields
        ------
        corr : :class:`numpy.array`
            Adjacent-layer correlations
        """
        depth = np.array([l.depth_mid for l in profile[:-1]])
        thick = np.diff(depth)
        depth = depth[1:]

        # Depth dependent correlation
        corr_depth = (self.rho_200 * np.power(
            (depth + self.rho_0) / (200 + self.rho_0), self.b))
        corr_depth[depth > 200] = self.rho_200

        # Thickness dependent correlation
        corr_thick = self.rho_0 * np.exp(-thick / self.delta)

        # Final correlation
        # Correlation coefficient
        corr = (1 - corr_depth) * corr_thick + corr_depth

        # Bedrock is perfectly correlated with layer above it
        corr = np.r_[corr, 1]

        return corr