org.apache.flink.api.java.summarize.NumericColumnSummary Maven / Gradle / Ivy

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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.flink.api.java.summarize;

import org.apache.flink.annotation.PublicEvolving;

/**
 * Generic Column Summary for Numeric Types.
 *
 * Some values are considered "missing" where "missing" is defined as null, NaN, or Infinity.
 * These values are ignored in some calculations like mean, variance, and standardDeviation.
 *
 * 
Uses the Kahan summation algorithm to avoid numeric instability when computing variance. The
 * algorithm is described in: "Scalable and Numerically Stable Descriptive Statistics in SystemML",
 * Tian et al, International Conference on Data Engineering 2012.
 *
 * @param  the numeric type e.g. Integer, Double
 */
@PublicEvolving
public class NumericColumnSummary extends ColumnSummary implements java.io.Serializable {

    private static final long serialVersionUID = 1L;

    private final long nonMissingCount; // count of elements that are NOT null, NaN, or Infinite
    private final long nullCount;
    private final long nanCount; // always zero for types like Short, Integer, Long
    private final long infinityCount; // always zero for types like Short, Integer, Long

    private final T min;
    private final T max;
    private final T sum;

    private final Double mean;
    private final Double variance;
    private final Double standardDeviation;

    public NumericColumnSummary(
            long nonMissingCount,
            long nullCount,
            long nanCount,
            long infinityCount,
            T min,
            T max,
            T sum,
            Double mean,
            Double variance,
            Double standardDeviation) {
        this.nonMissingCount = nonMissingCount;
        this.nullCount = nullCount;
        this.nanCount = nanCount;
        this.infinityCount = infinityCount;
        this.min = min;
        this.max = max;
        this.sum = sum;
        this.mean = mean;
        this.variance = variance;
        this.standardDeviation = standardDeviation;
    }

    /**
     * The number of "missing" values where "missing" is defined as null, NaN, or Infinity.
     *
     * 
These values are ignored in some calculations like mean, variance, and standardDeviation.
     */
    public long getMissingCount() {
        return nullCount + nanCount + infinityCount;
    }

    /** The number of values that are not null, NaN, or Infinity. */
    public long getNonMissingCount() {
        return nonMissingCount;
    }

    /** The number of non-null values in this column. */
    @Override
    public long getNonNullCount() {
        return nonMissingCount + nanCount + infinityCount;
    }

    @Override
    public long getNullCount() {
        return nullCount;
    }

    /**
     * Number of values that are NaN.
     *
     * 
(always zero for types like Short, Integer, Long)
     */
    public long getNanCount() {
        return nanCount;
    }

    /**
     * Number of values that are positive or negative infinity.
     *
     * 
(always zero for types like Short, Integer, Long)
     */
    public long getInfinityCount() {
        return infinityCount;
    }

    public T getMin() {
        return min;
    }

    public T getMax() {
        return max;
    }

    public T getSum() {
        return sum;
    }

    /**
     * Null, NaN, and Infinite values are ignored in this calculation.
     *
     * @see Arithmetic Mean
     */
    public Double getMean() {
        return mean;
    }

    /**
     * Variance is a measure of how far a set of numbers are spread out.
     *
     * 
Null, NaN, and Infinite values are ignored in this calculation.
     *
     * @see Variance
     */
    public Double getVariance() {
        return variance;
    }

    /**
     * Standard Deviation is a measure of variation in a set of numbers. It is the square root of
     * the variance.
     *
     * Null, NaN, and Infinite values are ignored in this calculation.
     *
     * @see Standard Deviation
     */
    public Double getStandardDeviation() {
        return standardDeviation;
    }

    @Override
    public String toString() {
        return "NumericColumnSummary{"
                + "totalCount="
                + getTotalCount()
                + ", nullCount="
                + nullCount
                + ", nonNullCount="
                + getNonNullCount()
                + ", missingCount="
                + getMissingCount()
                + ", nonMissingCount="
                + nonMissingCount
                + ", nanCount="
                + nanCount
                + ", infinityCount="
                + infinityCount
                + ", min="
                + min
                + ", max="
                + max
                + ", sum="
                + sum
                + ", mean="
                + mean
                + ", variance="
                + variance
                + ", standardDeviation="
                + standardDeviation
                + '}';
    }
}