I collected data on the growth of juvenile fish from 4 different types of crosses using multiple distinct family blocks and I am trying to see if cross type has an effect on growth using linear mixed effects models. I have one fixed factor (Length), 3 categorical random factors (sire, dam and sire/dam interaction) and a continuous random factor (density per tank). As I am relatively new to R and new to mixed effects models, I was wondering if I would have to code the continuous random factor in R differently from the categorical random factors using lme4?
So far I have
is density coded in properly, or would I have to alter it due to the fact that it is a continuous variable?