Lack-of-fit test for the mean structure based on cumulated residuals

The function provides a lack-of-fit test for the mean structure based on cumulated residuals from the model fit.

Usage

lin.test(
  object,
  noksSim = 20,
  seed = 20070325,
  plotit = TRUE,
  log = "",
  bp = 0.01,
  xlab,
  ylab,
  ylim,
  ...
)

Arguments

object: object of class 'drc'.
noksSim: numeric specifying the number of simulations used to obtain the p-value.
seed: numeric specifying the seed value for the random number generator.
plotit: logical indicating whether or not the observed cumulated residual process should be plotted. Default is to plot the process.
log: character string which should contain "x" if the x axis is to be logarithmic, "y" if the y axis is to be logarithmic and "xy" or "yx" if both axes are to be logarithmic. The empty string "" yields the original axes.
bp: numeric value specifying the break point below which the dose is zero.
xlab: character string specifying an optional label for the x axis.
ylab: character string specifying an optional label for the y axis.
ylim: numeric vector of length two, containing the lower and upper limit for the y axis.
...: additional arguments to be passed further to the basic plot method.

Value

A p-value for test of the null hypothesis that the mean structure is appropriate. Ritz and Martinussen (2009) provide the details.

Details

The function provides a graphical model checking of the mean structure in a dose-response model. The graphical display is supplemented by a p-value based on a supremum-type test.

The test is applicable even in cases where data are non-normal or exhibit variance heterogeneity.

References

Ritz, C and Martinussen, T. (2009) Lack-of-fit tests for assessing mean structures for continuous dose-response data, Submitted manuscript

Author

Christian Ritz

Examples

## Fitting a log-logistic model to the dataset 'etmotc'
etmotc.m1<-drm(rgr1~dose1, data=etmotc[1:15,], fct=LL.4())

## Test based on cumulated residuals
lin.test(etmotc.m1, 1000)

#> [1] 0.074