drc (version 2.3-96)

residuals.drc: Extracting residuals from the fitted dose-response model

Description

'residuals' extracts different types of residuals from an object of class 'drc'.

Usage

## S3 method for class 'drc':
residuals(object, typeRes = c("working", "standardised", "studentised"), 
  trScale = TRUE, ...)

Arguments

object

an object of class 'drc'.

typeRes

character string specifying the type of residual to be returned: raw/working residuals, residuals standardised using the estimated residual standard error, or studentised residuals based on the H matrix of partial derivatives of the model function.

trScale

logical value indicating whether or not to return residuals on the transformed scale (in case a Box-Cox transformation was applied).

...

additional arguments.

Value

• The raw (also called working) residuals or some kind of scaled residuals extracted from 'object'.

Details

Standardised residuals are the raw residuals divided by a scale estimate (if available). Studentised residuals are obtained by dividing by a scale estimate and in addition a correction factor (square root of 1 minus h with h is a diagonal element in the hat matrix).

Examples

## Fitting a four-parameter log-logistic model
ryegrass.m1 <- drm(rootl ~conc, data = ryegrass, fct = LL.4())

## Displaying the residual plot (raw residuals)
plot(fitted(ryegrass.m1), residuals(ryegrass.m1))

## Using the standardised residuals
plot(fitted(ryegrass.m1), residuals(ryegrass.m1, typeRes = "standard"))

## Overlayering the studentised residuals ... not much of a difference
points(fitted(ryegrass.m1), residuals(ryegrass.m1, typeRes = "student"), col = 2)