$$\frac{\boldsymbol w' \boldsymbol\sigma}{\boldsymbol{w' \Sigma w}}$$
Can the ratio above be simplified to one line, given that the weights could cancel somehow? $\boldsymbol{w}\in \mathbb{R}^{N\times 1}$ is a vector, $\boldsymbol\Sigma \in \mathbb{R}^{N\times N}$ is the covariance matrix, and $\boldsymbol\sigma \in \mathbb{R}^{N\times 1}$ is a vector of the elements $\sqrt{\text{diag}(\boldsymbol\Sigma)}$.