I try to reproduce Results from Harding and Pagan (2004), p.12, where they try to estimate the correlation coefficient $\rho_{S} = cor(S_{y,i},S_{x,i})$ using regression on
$$ \frac{S_{y,t}}{\hat{\sigma_{S_x}}\hat{\sigma_{S_y}}} = \alpha_1 + \frac{\rho_S}{\hat{\sigma_{S_x}}\hat{\sigma_{S_y}}} S_{x,t} + \varepsilon_{1,t} $$.
But whatever I try to transform the equations for linear relation between $S_{x,t}$, $S_{x,t}$
$$ S_{y,t} = \alpha_0+\beta S_{x,t}+\varepsilon_{0,t} $$
and the definition of the correlation coefficient $\hat{\beta} = \rho_S\frac{\hat{\sigma_{S_y}}}{\hat{\sigma_{S_x}}}$, I never manage to get the result in the first equation. Any ideas?
Thank's a lot!!