org.apache.mahout.classifier.df.ErrorEstimate.java Source code

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Here is the source code for org.apache.mahout.classifier.df.ErrorEstimate.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License 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 org.apache.mahout.classifier.df;

import com.google.common.base.Preconditions;

/**
 * Various methods to compute from the output of a random forest
 */
public final class ErrorEstimate {

    private ErrorEstimate() {
    }

    public static double errorRate(double[] labels, double[] predictions) {
        Preconditions.checkArgument(labels.length == predictions.length, "labels.length != predictions.length");
        double nberrors = 0; // number of instance that got bad predictions
        double datasize = 0; // number of classified instances

        for (int index = 0; index < labels.length; index++) {
            if (predictions[index] == -1) {
                continue; // instance not classified
            }

            if (predictions[index] != labels[index]) {
                nberrors++;
            }

            datasize++;
        }

        return nberrors / datasize;
    }

}