com.cloudera.science.ml.parallel.fn.SvmLightFn.java Source code

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Here is the source code for com.cloudera.science.ml.parallel.fn.SvmLightFn.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.parallel.fn;

import java.util.Iterator;
import java.util.Map;
import java.util.SortedMap;

import org.apache.crunch.MapFn;
import org.apache.mahout.math.NamedVector;
import org.apache.mahout.math.Vector;

import com.google.common.collect.Maps;

/**
 * Converts an input {@code Vector} type into an SVMLight-formatted string. For
 * {@code NamedVector} instances, the name of the vector will be written at the
 * head of the input.
 */
public class SvmLightFn<V extends Vector> extends MapFn<V, String> {
    @Override
    public String map(V v) {
        StringBuilder sb = new StringBuilder();
        if (v instanceof NamedVector) {
            sb.append(((NamedVector) v).getName()).append(' ');
        }
        Iterator<Vector.Element> iter = v.iterateNonZero();
        if (v.isSequentialAccess()) {
            if (iter.hasNext()) {
                Vector.Element first = iter.next();
                sb.append(first.index()).append(':').append(first.get());
            }
            while (iter.hasNext()) {
                Vector.Element e = iter.next();
                sb.append(' ').append(e.index()).append(':').append(e.get());
            }
        } else {
            SortedMap<Integer, Double> values = Maps.newTreeMap();
            while (iter.hasNext()) {
                Vector.Element e = iter.next();
                values.put(e.index(), e.get());
            }
            boolean first = true;
            for (Map.Entry<Integer, Double> e : values.entrySet()) {
                if (first) {
                    first = false;
                } else {
                    sb.append(' ');
                }
                sb.append(e.getKey()).append(':').append(e.getValue());
            }
        }
        return sb.toString();
    }
}