drc (version 3.0-1)

anova.drc: ANOVA for dose-response model fits

Description

'anova' produces an analysis of variance table for one or two non-linear model fits.

Usage

"anova"(object, ..., details = TRUE, test = NULL)

Arguments

object

an object of class 'drc'.

...

additional arguments.

details

logical indicating whether or not details on the models compared should be displayed. Default is TRUE (details are displayed).

test

a character string specifying the test statistic to be applied. Use "od" to assess overdispersion for binomial data.

Value

An object of class 'anova'.

Details

Specifying only a single object gives a test for lack-of-fit, comparing the non-linear regression model to a more general one-way or two-way ANOVA model. If two objects are specified a test for reduction from the larger to the smaller model is given. (This only makes statistical sense if the models are nested, that is: one model is a submodel of the other model.)

References

Bates, D. M. and Watts, D. G. (1988) Nonlinear Regression Analysis and Its Applications, New York: Wiley \& Sons (pp. 103--104)

See Also

For comparison of nested or non-nested model the function mselectcan also be used. The function anova.lm for linear models.

Examples

## Comparing a Gompertz three- and four-parameter models using an F test
ryegrass.m1 <- drm(rootl ~ conc, data = ryegrass, fct = W1.4())
ryegrass.m2 <- drm(rootl ~ conc, data = ryegrass, fct = W1.3())
anova(ryegrass.m2, ryegrass.m1)  # reduction to 'W1.3' not possible (highly significant)   

anova(ryegrass.m2, ryegrass.m1, details = FALSE)  # without details

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