org.talend.dataprep.transformation.aggregation.operation.Average.java Source code

Introduction

Here is the source code for org.talend.dataprep.transformation.aggregation.operation.Average.java

Source

//  ============================================================================
//
//  Copyright (C) 2006-2016 Talend Inc. - www.talend.com
//
//  This source code is available under agreement available at
//  https://github.com/Talend/data-prep/blob/master/LICENSE
//
//  You should have received a copy of the agreement
//  along with this program; if not, write to Talend SA
//  9 rue Pages 92150 Suresnes, France
//
//  ============================================================================

package org.talend.dataprep.transformation.aggregation.operation;

import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

import org.apache.commons.lang.StringUtils;
import org.talend.dataprep.api.dataset.row.DataSetRow;
import org.talend.dataprep.transformation.aggregation.api.AggregationResult;
import org.talend.dataprep.transformation.aggregation.api.WorkingContext;

/**
 * Average aggregator.
 */
public class Average extends AbstractAggregator implements Aggregator {

    /**
     * Count aggregator constructor. Package visible to ensure the use of the factory.
     * 
     * @param groupBy group by key.
     * @param columnId column id to aggregate.
     */
    Average(String groupBy, String columnId) {
        super(groupBy, columnId);
    }

    /**
     * @see java.util.function.BiConsumer#accept(Object, Object)
     */
    @Override
    public void accept(DataSetRow row, AggregationResult result) {
        final String key = row.get(groupBy);

        // init the group by in the result
        if (!result.contains(key)) {
            result.put(key, new AverageContext());
        }

        final AverageContext context = (AverageContext) result.get(key);
        context.process(row.get(columnId));
    }

    @Override
    public void normalize(AggregationResult result) {
        // Remove from result all entries with NaN as average.
        Set<String> entryToRemove = result.entries().stream()
                .filter(entry -> Double.isNaN(entry.getValue().getValue())).map(Map.Entry::getKey)
                .collect(Collectors.toSet());
        entryToRemove.forEach(result::remove);
    }

    /**
     * Working context for average.
     */
    class AverageContext implements WorkingContext {

        /** How many occurrences. */
        private long count;

        /** Sum of the occurrences. */
        private double sum;

        /**
         * Constructor that initialize the context.
         */
        AverageContext() {
            this.count = 0;
            this.sum = 0;
        }

        /**
         * Update the context with the given value.
         * 
         * @param value the row value to process.
         */
        void process(String value) {
            // skip null or empty value
            if (StringUtils.isEmpty(value)) {
                return;
            }

            double newAmount;
            try {
                newAmount = Double.parseDouble(value);
            } catch (NumberFormatException e) {
                // skip non number
                return;
            }

            sum += newAmount;
            count++;
        }

        /**
         * @see WorkingContext#getValue()
         */
        @Override
        public double getValue() {
            return sum / count;
        }

    }
}