hqmisc (version 0.2-1)

as.dummies: Create matrix of dummy vectors from single factor

Description

Create a matrix of dummy vectors (consisting of 0 and 1 only) from factor x. This may be useful if you want to use dummy predictors in regression analysis.

Usage

as.dummies ( x )

Arguments

x

input factor. If the argument is not a factor, the function stops with a message.

Value

Matrix of integer values 0 or 1. The number of rows of the returned matrix equals the length of the input factor, and the number of columns equals the number of levels of the input factor.

Details

Levels of the input factor correspond with columns in the output matrix. The integer value in cell [i,j] of the returned matrix indicates whether (value=1) or not (value=0) the i'th observation in the input factor x has the value of the j'th level of that factor.

as.dummies(x) is similar to model.matrix(~-1+x).

See Also

levels, matrix, model.matrix..

Examples

# NOT RUN {
xf <- factor( rep(letters[1:3],each=2) )
as.dummies(xf)
# }