Update and Re-fit a Model Call

Usage

update(object, ...)
update.default(object, formula, ..., evaluate = TRUE)

Arguments

object An existing fit from a model function such as lm, glm and many others.
formula Changes to the formula – see update.formula for details.
... Additional arguments to the call, or arguments with changed values. Use name=NULL to remove the argument name.
evaluate If true evaluate the new call else return the call.

Description

update will update and (by default) re-fit a model. It does this by extracting the call stored in the object, updating the call and (by default) evaluating that call. Sometimes it is useful to call update with only one argument, for example if the data frame has been corrected.

Value

If evaluate = TRUE the fitted object, otherwise the updated call.

Author(s)

B.D. Ripley

See Also

update.formula

Examples

oldcon <- options(contrasts = c("contr.treatment", "contr.poly"))
## Annette Dobson (1990) "An Introduction to Statistical Modelling".
## Page 9: Plant Weight Data.
ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)
trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
group <- gl(2, 10, 20, labels = c("Ctl", "Trt"))
weight <- c(ctl, trt)
lm.D9 <- lm(weight ~ group)
lm.D9
summary(lm.D90 <- update(lm.D9, . ~ . - 1))
options(contrasts = c("contr.helmert", "contr.poly"))
update(lm.D9)
options(oldcon)

[Package Contents]