makegrowthObjHossfeld:
Function to make a Hossfeld Growth Object
Description
Takes a data-frame with at minimum columns size and sizeNext; and fits a Hossfeld type growth function
to increment - if length(dataf$incr) is zero, it will calculate dataf$increment as the difference between
size and sizeNext; otherwise it will take the column provided
Usage
makegrowthObjHossfeld(dataf)
Arguments
dataf
a dataframe with columns `size' and
`sizeNext'(`size' is size at t, `sizeNext' is size at t+1);
Value
Returns a growth object of class growthObjHossfeld for which growth methods exist.