BernoulliLikelihood.java

package cs475;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Scanner;

import org.apache.commons.cli.Option;
import org.apache.commons.cli.OptionBuilder;

public class BernoulliLikelihood {
	static public LinkedList<Option> options = new LinkedList<Option>();
	
	public static void main(String[] args) throws IOException {
		// Parse the command line.
		String[] manditory_args = { "data"};
		createCommandLineOptions();
		CommandLineUtilities.initCommandLineParameters(args, BernoulliLikelihood.options, manditory_args);
		
		String dataFile = CommandLineUtilities.getOptionValue("data");
		BernoulliLikelihood bl = new BernoulliLikelihood();
		ArrayList<Integer> data = bl.readData(dataFile);
		
		double parameter = bl.computeMaximumLikelihood(data);
		double llhood = bl.computeLogLikelihood(data, parameter);
		System.out.println("Maximum Likelihood Solution: " + Double.toString(parameter));
		System.out.println("Log-likelihood: " + Double.toString(llhood));

		
	}
	
	public static void registerOption(String option_name, String arg_name, boolean has_arg, String description) {
		OptionBuilder.withArgName(arg_name);
		OptionBuilder.hasArg(has_arg);
		OptionBuilder.withDescription(description);
		Option option = OptionBuilder.create(option_name);
		
		BernoulliLikelihood.options.add(option);		
	}
	
	private static void createCommandLineOptions() {
		registerOption("data", "String", true, "The data file to read.");
	}
	
	public double computeMaximumLikelihood(ArrayList<Integer> data) {
		// TODO: Fill in here
//		float result = 0;
		int sum = 0;
		for(int i=0; i<data.size();i++){
			sum = sum + data.get(i);
//			System.out.println(data.get(i));
		}
//		result = (float)sum/data.size();
//		System.out.println(result);
		return (double)sum/data.size();
		
	}
	
	public double computeLogLikelihood(ArrayList<Integer> data, double parameter) {
		// TODO: Fill in here
		int n = data.size();
		int sum = 0;
		for(int i=0; i<data.size();i++){
			sum = sum + data.get(i);
		}
//		double y = computeMaximumLikelihood(data);
		double result = sum*Math.log(parameter)+(data.size()-sum)*Math.log(1-parameter);
		return result;
	}
	
	public ArrayList<Integer> readData(String filename) throws FileNotFoundException {
		Scanner scanner = new Scanner(new BufferedInputStream(new FileInputStream(filename)));
		ArrayList<Integer> data = new ArrayList<Integer>();
		
		while (scanner.hasNextLine()) {
			String line = scanner.nextLine();
			if (line.trim().length() == 0)
				   continue;
			String result = line.trim();
			int value = Integer.parseInt(result);
			data.add(value);
		}
		
		scanner.close();
		return data;
	}
}