DescTools (version 0.99.9)

Dummy: Generate Dummy Codes for a Factor

Description

Generates a matrix of dummy codes (class indicators) for a given factor.

Usage

Dummy(x, method = c("treatment", "sum", "helmert", "poly", "full"), base = 1)

Arguments

x

factor or vector of classes for cases.

method

defines the method of the contrasts being formed. Can be one out of "treatment", "sum", "helmert", "poly", "full", whereas "treatment" is the default one. Abbreviations

base

an integer specifying which group is considered the baseline group.

Value

• a matrix with the dummy codes. The rows correspond to the number of elements in x and the columns to it's levels.

References

Venables, W N and Ripley, B D (2002): Modern Applied Statistics with S. Fourth edition. Springer.

See Also

model.frame, contrasts, class.ind in the package nnet

Examples

x <- c("red","blue","green","blue","green","red","red","blue") 
Dummy(x) 
Dummy(x, base = 2)

Dummy(x, method = "sum")


y <- c("Max","Max","Max","Max","Max","Bill","Bill","Bill")

Dummy(y) 
Dummy(y, base = "Max")

Dummy(y, base = "Max", method="full")


# "Undummy" (revert the dummy coding) 
m <- Dummy(y, method="full")
m
z <- apply(m, 1, function(x) colnames(m)[x==1])
z
identical(y, as.vector(z))

m <- Dummy(y)
m
z <- apply(m, 1, function(x) ifelse(sum(x)==0, attr(m,"base"), colnames(m)[x==1]))
z