expGrowth {rSHAPE}

This function uses the exponential growth model and can either calculated the expected growth for a single time step OR it can work backwards to calculated what was the expected starting population size prior to a step of exponential growth.

Description

This function uses the exponential growth model and can either calculated the expected growth for a single time step OR it can work backwards to calculated what was the expected starting population size prior to a step of exponential growth.

Usage

expGrowth(func_rate, func_step, func_startPop = NULL,
  func_endPop = NULL)

Arguments

func_rate

This is the number of offpsring expected to be produced by an individual. When calculating the expected population size after a time step, we force this rate to be no less than 1 since this function has meaning only in the birth function and so we do not want to calculate negative births (which would mean deaths).

func_step

This is a proportional scalar that will control what proportion of a standard "generation" is simulated for each step within a SHAPE run. NOTE: This parameter is not perfectly validated to run as may be expected with all models. For now, it should be left as a value of "1", but exists for future implementation and testing.

func_startPop

This is the initial population size(s) for which you want to calculate a final size. Leave NULL if trying to calculated the expected initial size from a final population.

func_endPop

This is the final population size(s) for which you want to calculate a initial size. Leave NULL if trying to calculated the expected final size from an initial population.

Value

numeric value

Examples

# Exponential growth equation implemented but allowing either the final or initial population
# to be calculated based on whethere the initial or final community size is input.
expGrowth(func_rate = 2, func_step = 1,func_startPop = 100)
expGrowth(func_rate = 2, func_step = 1,func_endPop = 200)
expGrowth(func_rate = 2, func_step = 7,func_startPop = 100)
# You cannot set a growth rate less than 1 as this would then simulate deaths which is not
# allowed in this calculation.
expGrowth(func_rate = c(0.9,1,1.1), func_step = 1,func_startPop = 100)