Class LevelIndicators

src/com/winvector/variables/LevelIndicators.java:19–118

The standard way to encode a categorical variable- build one indicator function per value (we don't supress one level). @author johnmount

 *
 */
public final class LevelIndicators implements VariableMapping {
	private static final long serialVersionUID = 1L;
	
	private final String origColumn;
	private final int index;
	private final Map<String,Integer> levelCodes = new HashMap<String,Integer>();
	
	public LevelIndicators(final String origColumn, final int index, final Collection<String> levels) {
		this.origColumn = origColumn;
		this.index = index;
		for(final String li: new TreeSet<String>(levels)) {
			levelCodes.put(li,levelCodes.size());
		}
	}
	
	public Set<String> levels() {
		return levelCodes.keySet();
	}
	
	public int index(final String level) {
		return index + levelCodes.get(level);
	}
	
	@Override
	public String origColumn() {
		return origColumn;
	}

	@Override
	public int indexL() {
		return index;
	}

	@Override
	public int indexR() {
		return index + levelCodes.size();
	}
	
	@Override
	public boolean wantRegularization() {
		return false;
	}

	@Override
	public void process(final BurstMap row, final double[] vec) {
		final String level = row.getAsString(origColumn);
		if(level!=null) {
			final Integer code = levelCodes.get(level);
			if(code!=null) {
				vec[index+code] = 1.0;	
			}
		}
	}

	@Override
	public String name() {
		return "CategoricalLevels";
	}