'baro5' allows specification of the baroreflex 5-parameter dose response function, under various constraints on the parameters.
baro5(fixed = c(NA, NA, NA, NA, NA), names = c("b1", "b2", "c", "d", "e"),
method = c("1", "2", "3", "4"), ssfct = NULL)The value returned is a list containing the nonlinear model function, the self starter function and the parameter names.
numeric vector. Specifies which parameters are fixed and at what value they are fixed. NAs for parameter that are not fixed.
a vector of character strings giving the names of the parameters (should not contain ":"). The order of the parameters is: b1, b2, c, d, e (see under 'Details').
character string indicating the self starter function to use.
a self starter function to be used.
Christian Ritz
The five-parameter function given by the expression
$$ y = c + \frac{d-c}{1+f\exp(b1(\log(x)-\log(e))) + (1-f)\exp(b2(\log(x)-\log(e)))}$$
$$ f = 1/( 1 + \exp((2b1b2/|b1+b2|)(\log(x)-\log(e))))$$
If the difference between the parameters b1 and b2 is different from 0 then the function is asymmetric.
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.