Extracting residuals from the fitted dose-response model

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

# S3 method for 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).

Note

The 'standardised' residuals are available for least squares estimation with or without Box-Cox transformation or variance as a power of the mean.

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)