R: Create dummy coded variables

dummy.code {psych} | R Documentation

## Create dummy coded variables

### Description

Given a variable x with n distinct values, create n new dummy coded variables coded 0/1 for presence (1) or absence (0) of each variable. A typical application would be to create dummy coded college majors from a vector of college majors.

### Usage

    dummy.code(x)

### Arguments

`x` | A vector to be transformed into dummy codes

### Details

When coding demographic information, it is typical to create one variable with multiple categorical values (e.g., ethnicity, college major, occupation). `dummy.code` will convert these categories into n distinct dummy coded variables.

If using dummy coded variables as predictors, remember to use n-1 variables.

### Value

A matrix of dummy coded variables

### Author(s)

William Revelle

### Examples

    new <- dummy.code(sat.act$education)
    new.sat <- data.frame(new,sat.act)
    round(cor(new.sat,use="pairwise"),2)

[Package psych version 1.7.8 Index]