Takes AR1 values and transforms them to GM

ar1_to_gm(theta, freq)

## Arguments

theta

A vec that contains AR1 values.

freq

A double indicating the frequency of the data.

## Value

A vec containing GM values.

## Details

The function takes a vector of AR1 values $$\phi$$ and $$\sigma ^2$$ and transforms them to GM values $$\beta$$ and $$\sigma ^2_{gm}$$ using the formulas: $$\beta = - \frac{{\ln \left( \phi \right)}}{{\Delta t}}$$ $$\sigma _{gm}^2 = \frac{{{\sigma ^2}}}{{1 - {\phi ^2}}}$$

James Balamuta