pymc.gp.cov.ExpQuad.功率谱密度

ExpQuad.power_spectral_density(omega)

ExpQuad 核的功率谱密度为：

\[S(\boldsymbol\omega) = (\sqrt(2 \pi)^D \prod_{i}^{D}\ell_i \exp\left( -\frac{1}{2} \sum_{i}^{D}\ell_i^2 \omega_i^{2} \right)\]