R: Multistage dose-response model with quadratic terms

multi2 {drc} | R Documentation

## Multistage dose-response model with quadratic terms

### Description

The multistage dose-response model is a combination of log-logistic models that should be useful for describing more complex dose-response patterns.

### Usage

      multi2(
      fixed = c(NA, NA, NA, NA, NA),
      names = c("b1", "b2", "b3", "c", "d"),
      ssfct = NULL,
      fctName,
      fctText)

### Arguments

`fixed` | numeric vector specifying which parameters are fixed and at what value they are fixed. NAs are used for parameters 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').
`ssfct` | a self starter function to be used.
`fctName` | optional character string used internally by convenience functions.
`fctText` | optional character string used internally by convenience functions.

### Details

The multistage model function with quadratic terms is defined as follows

f(x) = c + (d-c)\exp(-b1-b2x-b3x^2)

where x denotes the dose or the logarithm-transformed dose.

### Value

The value returned is a list containing the nonlinear function, the self starter function and the parameter names.

### Author(s)

Christian Ritz

### References

Wheeler, M. W., Bailer, A. J. (2009) Comparing model averaging with other model selection strategies for benchmark dose estimation, Environmental and Ecological Statistics, 16, 37–51.

[Package drc version 3.0-1 Index]