AllLab_Skeleton.Lab4.Lab4_Std_dev.java Source code

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Here is the source code for AllLab_Skeleton.Lab4.Lab4_Std_dev.java

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/*
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package AllLab_Skeleton.Lab4;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import static java.util.Collections.list;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

/**
 *
 * @author pooja
 */
public class Lab4_Std_dev {

    /**
     * @param args the command line arguments
     */
    public static class Map extends Mapper<Object, Text, Text, DoubleWritable> {

        public void map(Object key, Text value, Context context) {
            try {
                String row[] = value.toString().split(",");
                String stock = row[1];
                String price = row[4];
                double pri = Double.parseDouble(price);

                context.write(new Text(stock), new DoubleWritable(pri));

            } catch (Exception e) {

            }
        }
    }

    public static class Reduce extends Reducer<Text, DoubleWritable, Text, MedianSDCustomWritable> {

        private MedianSDCustomWritable result = new MedianSDCustomWritable();
        private ArrayList<Double> list = new ArrayList<Double>();

        public void reduce(Text key, Iterable<DoubleWritable> values, Context context)
                throws IOException, InterruptedException {

            double sum = 0;
            double count = 0;
            list.clear();
            result.setStandardDeviation(0);

            for (DoubleWritable val : values) {
                list.add(val.get());
                sum += val.get();
                count++;
            }

            Collections.sort(list);

            if (count % 2 == 0) {
                result.setMedian((list.get((int) count / 2) + list.get((int) count / 2 - 1)) / 2);

            } else {
                result.setMedian(list.get((int) count / 2));
            }

            double mean = sum / count;
            double sumOfSquares = 0;

            for (double val : list) {
                sumOfSquares += (val - mean) * (val - mean);
            }
            result.setStandardDeviation((double) Math.sqrt(sumOfSquares / (count - 1)));
            context.write(key, result);
        }
    }

    public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf, "medianstd");
        job.setJarByClass(Lab4_Std_dev.class);
        job.setMapperClass(Map.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(DoubleWritable.class);

        job.setReducerClass(Reduce.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(MedianSDCustomWritable.class);
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        System.exit(job.waitForCompletion(true) ? 0 : 1);

    }

}