drc (version 1.2-0)

baro5: The modified baro5 function

Description

'baro5' allows specification of the baroreflex 5-parameter dose response function, under various constraints on the parameters.

Usage

baro5(lowerc = c(-Inf, -Inf, -Inf, -Inf, -Inf), 
upperc = c(Inf, Inf, Inf, Inf, Inf), fixed = c(NA, NA, NA, NA, NA), 
names = c("b1", "b2", "c", "d", "e"), scaleDose = TRUE, useDer = FALSE)

Arguments

lowerc

numeric vector. The lower bound on parameters. Default is minus infinity.

upperc

numeric vector. The upper bound on parameters. Default is plus infinity.

fixed

numeric vector. Specifies which parameters are fixed and at what value they are fixed. NAs for parameter that are not fixed.

names

a vector of character strings giving the names of the parameters (should not contain ":"). The default is reasonable (see under 'Usage'). The order of the parameters is: b1, b2, c, d, e (see under 'Details').

scaleDose

logical. If TRUE dose values are scaled around 1 during estimation; this is required for datasets where all dose values are small.

useDer

logical. If TRUE derivatives are supplied, otherwise they are not supplied. Not implemented.

Value

• The value returned by the 'baro5' is a list with the following components
• fct
  The dose response function.
• ssfct
  The self starter function.
• deriv1
  The first derivative. Not available.
• deriv2
  The second derivative. Not available.
• lowerc
  The lower bounds on the parameters.
• upperc
  The upper bounds on the parameters.
• edfct
  The ED function. Not available.
• sifct
  The SI function. Not available.

Details

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.

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.

Examples

## See the example for the heartrate dataset