Exponential decay model with or without a nonzero lower limit.

meEXD.2(x, d, e)

meEXD.3(x, c, d, e)

Arguments

x	numeric dose vector
d	upper limit
e	steepness
c	lower limit

Details

The exponential decay model is a three-parameter model with mean function: $$f(x) = c + (d-c)(\exp(-x/e))$$ The parameter init is the upper limit (attained at $x=0$), the parameter plateau is the lower limit reached for x going to infinity and the parameter $e>0$ is determining the steepness of the decay. The curve is monotonously decreasing in $x$.

References

Organisation for Economic Co-operation and Development (OECD) (2006) Current approaches in the statistical analysis of ecotoxicity data: A guidance to application - annexes, Paris: OECD (p. 80).