R: Gamma dose-response model

gammadr {drc} | R Documentation

## Gamma dose-response model

### Description

The gamma dose-response model is a four-parameter model derived from the cumulative distribution function of the gamma distribution.

### Usage

      gammadr(fixed = c(NA, NA, NA, NA),
      names = c("b", "c", "d", "e"), 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').
`fctName` | optional character string used internally by convenience functions.
`fctText` | optional character string used internally by convenience functions.

### Details

Following Wheeler and Bailer (2009) the model function is defined as follows:

f(x) = c + (d-c) * pgamma(b*x, e, 1)

This model is only suitable for increasing dose-response data.

### 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]