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Wrapper for 5-parameter Cedergreen-Ritz-Streibig Model

Source: R/cedergreen.R
CRS.5.Rd

A convenience wrapper for the drc::cedergreen function, preset for a 5-parameter model. It provides flexible handling for the alpha parameter.

Usage

CRS.5(
  names = c("b", "c", "d", "e", "f"),
  fixed = c(NA, NA, NA, NA, NA),
  alpha_type = "a",
  fctName = NULL,
  fctText = NULL,
  ...
)

Arguments

names

A character vector of length 5 specifying the names of the model parameters. Default is c("b", "c", "d", "e", "f").

fixed

A numeric vector of length 5. Use NA for parameters to be estimated and a numeric value for parameters to be fixed. Default is all NA.

alpha_type

A character or a numeric value. Can be one of 'a' (alpha=1), 'b' (alpha=0.5), 'c' (alpha=0.25), or a specific numeric value for alpha.

fctName

An optional character string to name the model function. If NULL (the default), a name is generated automatically.

fctText

An optional character string describing the model. If NULL (the default), a description is generated automatically.

...

Additional arguments to be passed to drc::cedergreen, such as data.

Value

A drc model object of class cedergreen. If the underlying drc::cedergreen call fails, it issues a warning and returns NULL.

Details

This function simplifies the creation of a 5-parameter Cedergreen-Ritz-Streibig model by setting sensible defaults for the parameter names. It allows the alpha parameter to be specified either by a predefined character shortcut ('a', 'b', 'c') or by a direct numeric value.

By default the function runs with alpha=1, which corresponds to the CRS.4a model. Setting alpha=0.5 corresponds to the CRS.4b model, and alpha=0.25 corresponds to the CRS.4c model.

By default, all parameters are set to be estimated (i.e., fixed is all NA), but users can specify any parameters to be held constant during estimation. The self-starter function is automatically generated based on the specified method and fixed parameters, ensuring that initial values are appropriately calculated for the model fitting process.

The function automatically generates a model name (fctName) and description (fctText) unless they are explicitly provided by the user.

Author

Hannes Reinwald

Examples

# Create a CRS.5 model specification
crs_model_a <- CRS.5()

# Fix the lower limit to 0 and use a custom numeric alpha
crs_model_custom <- CRS.5(
  fixed = c(NA, 0, NA, NA, NA), alpha_type = 0.75
)