feat_growth: Adds an exponential growth or decline of the size of one
population to a model.
Description
This function changes the growth factor of a population at given
point in time (time). This factor than applies to the time
interval farther into the past from this point.
The time at which the population starts to grow or decline.
Value
The demographic model with a size change.
Details
The population size changes by factor exp(-alpha*t), where alpha
is the growth parameter and t is the time since the growth has
started. Hence, for positive alpha, the population will decline
backwards in time or grow forwards in time. Similar, will decline
in forwards time for a negative value of alpha.
If you want to add an instantaneous change of the population size,
then use the feat_size_change function.