Researchers often need to calculate body-size growth rates for individuals
that do not have associated age data. These growth rates are based on
mark-recapture data where an individual was captured and measured at time 1
then recaptured and measured at time 2. The sizes at each time and amount
of time between captures can be used to calculate growth rates. 'MRgrowth'
follows the approach in Edmonds et al. (2021)