expand.model.frame
Add new variables to a model frame
Description
Evaluates new variables as if they had been part of the formula of the specified model. This ensures that the same na.action
and subset
arguments are applied and allows, for example, x
to be recovered for a model using sin(x)
as a predictor.
Usage
expand.model.frame(model, extras, envir = environment(formula(model)), na.expand = FALSE)
Arguments
model | a fitted model |
extras | one-sided formula or vector of character strings describing new variables to be added |
envir | an environment to evaluate things in |
na.expand | logical; see below |
Details
If na.expand = FALSE
then NA
values in the extra variables will be passed to the na.action
function used in model
. This may result in a shorter data frame (with na.omit
) or an error (with na.fail
). If na.expand = TRUE
the returned data frame will have precisely the same rows as model.frame(model)
, but the columns corresponding to the extra variables may contain NA
.
Value
A data frame.
See Also
Examples
model <- lm(log(Volume) ~ log(Girth) + log(Height), data = trees) expand.model.frame(model, ~ Girth) # prints data.frame like dd <- data.frame(x = 1:5, y = rnorm(5), z = c(1,2,NA,4,5)) model <- glm(y ~ x, data = dd, subset = 1:4, na.action = na.omit) expand.model.frame(model, "z", na.expand = FALSE) # = default expand.model.frame(model, "z", na.expand = TRUE)
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Licensed under the GNU General Public License.