com.cloudera.science.ml.core.formula.Term.java Source code

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Here is the source code for com.cloudera.science.ml.core.formula.Term.java

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/**
 * Copyright (c) 2013, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, Inc. licenses this file to you under the Apache License,
 * Version 2.0 (the "License"). You may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, either express or implied. See the License for
 * the specific language governing permissions and limitations under the
 * License.
 */
package com.cloudera.science.ml.core.formula;

import java.util.Arrays;
import java.util.Iterator;
import java.util.Set;

import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;

public class Term implements Iterable<String>, Comparable<Term> {

    public static final Term INTERCEPT = new Term();

    private final Set<String> names;

    public static Term $(String... names) {
        return new Term(names);
    }

    public Term(String... names) {
        this.names = Sets.newTreeSet(Arrays.asList(names));
        Preconditions.checkArgument(!this.names.isEmpty(), "Terms must have >= 1 named variables");
    }

    private Term() {
        // private constructor for the intercept term
        this.names = ImmutableSet.of();
    }

    public boolean isIntercept() {
        return names.isEmpty();
    }

    public boolean hasInteractions() {
        return names.size() > 1;
    }

    @Override
    public Iterator<String> iterator() {
        return names.iterator();
    }

    @Override
    public String toString() {
        if (names.isEmpty()) {
            return "Intercept";
        }
        return Joiner.on(':').join(names);
    }

    @Override
    public boolean equals(Object other) {
        if (!(other instanceof Term)) {
            return false;
        }
        Term t = (Term) other;
        return names.equals(t.names);
    }

    @Override
    public int hashCode() {
        return names.hashCode();
    }

    @Override
    public int compareTo(Term t) {
        int thisSize = names.size();
        int otherSize = t.names.size();
        if (thisSize == otherSize) {
            // Compare elements
            Iterator<String> me = names.iterator();
            Iterator<String> them = t.names.iterator();
            while (me.hasNext() && them.hasNext()) {
                int diff = me.next().compareTo(them.next());
                if (diff != 0) {
                    return diff;
                }
            }
            return 0;
        }
        return thisSize < otherSize ? -1 : 1;
    }
}