Convenience function to convert a growth rate (little r)
to a reproduction number (R) given a particular
generation time.

Usage,

`r2R(r, mu_gamma = 4.7, sd_gamma = 2.9)`

## Arguments

- r
a double representing the growth rate

- mu_gamma
a double representing mean of the
gamma function characterizing the generation time.

- sd_gamma
a double representing standard deviation of the
gamma function characterizing the generation time.

## Examples

```
cases <- rpois(10,2.5)
t <- 1:10
fit <- glm(cases ~ t, family = "poisson")
r2R(coef(fit)[2])
#> t
#> 0.759288
```