update {base}

R Documentation

Update and Re-fit a Model 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.

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.

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 Generalized Linear Models".
## 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)

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