Brian Jackson edited Ultimately_we_are_interested_in__.tex  over 8 years ago

Commit id: 6d5f4852761d0095b16dcdc4d9684730e13da718

deletions | additions      

       

Ultimately, we are interested in converting the density of observed to the density of actual parameters. Fortunately, Equation \ref{eqn:convert_from_actual_to_observed_density} provides a simple way of working from the observed to the actual distribution of physical parameters. Differentiating with respect to $b(\Gamma_{\rm obs}, P_{\rm obs})$ and then solving for $\rho(\Gamma_{\rm act}(b), P_{\rm act}(b)) act}(b))$  gives \begin{equation}  \label{eqn:convert_from_observed_to_actual_density}  \rho(\Gamma_{\rm act}(b), P_{\rm act}(b)) = \frac{1}{2} b_{\rm max}^2 f(b) \dfrac{d\rho(\Gamma_{\rm obs}, P_{\rm obs}}{db}  \end{equation}  It's clear that plugging Equation \ref{eqn:n-Pobs_from_uniform_n-Pact} into Equation \ref{eqn:n-Pact_from_n-Pobs} recovers the original uniform distribution. On the surface, though, Equation \ref{eqn:n-Pact_from_n-Pobs} suggests the strange result that for the power-law distribution $n(P_{\rm obs}) \sim P_{\rm obs}^{-2}$, similar to that reported in \citet{Jackson_2015}, the underlying distribution $n(P_{\rm obs}) = 0$. However, the approach here assumes that $P_{\rm obs}$-values only span a finite range, which is violated by the simple $P_{\rm obs}^{-2}$ power-law. Instead, a form similar to Equation \ref{eqn:n-Pobs_from_uniform_n-Pact} can be used to describe a power-law, with the 2 replaced by the desired index.