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Construct design matrices

Syntax

model.matrix(formula=, data=)

Arguments

formula A model formula or terms object
data A data frame created with model.frame

Description

Creates a design matrix from the description given in terms(formula), using the data in data. data must contain columns with the same names as would be created by a call to model.frame(formula) or, more precisely, by evaluating attr(terms(formula),"variables"). There may be other columns and the order is not important.

Value

The design matrix for a regression model with the specified formula and data.

References

Chambers and Hastie: "Statistical Models in S"

See Also

model.frame, LANK(model.data.frame), LANK(terms)

Examples

data(trees) ff<-log(Volume)~log(Height)+log(Girth) m<-model.frame(ff,trees) mat<-model.matrix(ff,m)