org.arbeitspferde.groningen.common.Statistics.java Source code

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Here is the source code for org.arbeitspferde.groningen.common.Statistics.java

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/* Copyright 2012 Google, Inc.
 *
 * Licensed 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.arbeitspferde.groningen.common;

import com.google.common.base.Preconditions;

import java.util.Collections;
import java.util.List;
import java.util.logging.Logger;

/**
 * The Groningen statistics class contains all the specialized statistics routines
 * required to support functionality such as scoring latency.
 *
 *
 * TODO(team) implement linear interpolation, or use com.google.math.Rank
 */
public class Statistics {
    /** Logger for this class */
    private static final Logger log = Logger.getLogger(Statistics.class.getCanonicalName());

    /**
     * Compute the input percentile of the input double {@link List}. Returns
     * Double.NaN if the list of values is empty.
     *
     * Keep in mind that the values are sorted in place, thus modifying the values
     * {@link List} you've passed in.
     *
     * @param {@link Double} {@link List}
     * @param double percentile
     */
    public static double computePercentile(List<Double> values, double percentile) {
        Preconditions.checkArgument(percentile >= 0, "percentile must be greater or equal than 0");
        Preconditions.checkArgument(percentile <= 100, "percentile must be smaller or equal than 100");

        int sz = values.size();
        switch (sz) {
        case 0:
            log.warning("The list passed to computePercentile is empty. NaN returned.");
            return Double.NaN;
        case 1:
            return values.get(0);
        default:
            // Sort {@link List} in place and in ascending order
            Collections.sort(values);
            // the 100th percentile is defined to be the largest value
            if (percentile == 100) {
                return values.get(sz - 1);
            }
            return values.get((int) Math.floor(percentile * (double) sz / 100.0));
        }
    }
}