The Baroreflex Five-Parameter Dose-Response Model

baro5 provides the five-parameter baroreflex model function, allowing specification under various parameter constraints. The model accommodates asymmetric dose-response curves.

Usage

baro5(
  fixed = c(NA, NA, NA, NA, NA),
  names = c("b1", "b2", "c", "d", "e"),
  method = c("1", "2", "3", "4"),
  ssfct = NULL
)

Arguments

fixed: numeric vector. Specifies which parameters are fixed and at what value they are fixed. NAs for parameters that are not fixed.
names: a vector of character strings giving the names of the parameters (should not contain ":"). The order is: b1, b2, c, d, e.
method: character string indicating the self starter function to use.
ssfct: a self starter function to be used.

Value

A list containing the nonlinear model function, the self starter function, and the parameter names.

Details

The five-parameter function is given by:

$$y = c + \frac{d-c}{1+f\exp(b1(\log(x)-\log(e))) + (1-f)\exp(b2(\log(x)-\log(e)))}$$

$$f = 1/(1 + \exp((2b1 b2/|b1+b2|)(\log(x)-\log(e))))$$

If the difference between b1 and b2 is nonzero, the function is asymmetric.

References

Ricketts, J. H. and Head, G. A. (1999) A five-parameter logistic equation for investigating asymmetry of curvature in baroreflex studies. Am. J. Physiol. (Regulatory Integrative Comp. Physiol. 46), 277, 441–454.

Author

Christian Ritz