R: Neill's lack-of-fit test for dose-response models

neill.test {drc} | R Documentation

## Neill's lack-of-fit test for dose-response models

### Description

'neill.test' provides a lack-of-fit test for non-linear regression models. It is applicable both in cases where there are replicates (in which case it reduces to the standard lack-of-fit test against an ANOVA model) and in cases where there are no replicates, though then a grouping has to be provided.

### Usage

      neill.test(object, grouping, method = c("c-finest", "finest", "percentiles"),
      breakp = NULL, display = TRUE)

### Arguments

`object` | object of class 'drc' or 'nls'.
`grouping` | character or numeric vector that provides the grouping of the dose values.
`method` | character string specifying the method to be used to generate a grouping of the dose values.
`breakp` | numeric vector of break points for generating dose intervals that form a grouping.
`display` | logical. If TRUE results are displayed. Otherwise they are not (useful in simulations).

### Details

The functions used the methods `df.residual` and `residuals` and the 'data' component of `object` (only for determining the number of observations).

### Value

The function returns an object of class anova which is displayed using `print.anova`.

### Note

A clustering technique could be employed to determine the grouping to be used in cases where there are no replicates. There should at most be ceiling(n/2) clusters as otherwise some observations will not be used in the test. At the other end there need to be more clusters than parameters in the model.

### Author(s)

Christian Ritz

### References

Neill, J. W. (1988) Testing for lack of fit in nonlinear regression, Ann. Statist., 16, 733–740

### See Also

See also `modelFit` for details on the lack-of-fit test against an ANOVA model.

### Examples

    ### Example with 'drc' object

    ## Lack-of-fit test against ANOVA
    ryegrass.m1 <-drm(rootl~conc, data = ryegrass, fct = LL.4())
    modelFit(ryegrass.m1)

    ## The same test using 'neill.test'
    neill.test(ryegrass.m1, ryegrass$conc)

    ## Generating a grouping
    neill.test(ryegrass.m1, method="c-finest")
    neill.test(ryegrass.m1, method="finest")
    neill.test(ryegrass.m1, method="perc")

[Package drc version 3.0-1 Index]