ComputeDeviation

ComputeDeviation.java

/*
 * Name: Nikolay Ostroukhov
 * Date: 11/9/19
 * Course Number: 111
 * Course Name: CSC
 * Problem Number: Homework 8 -- Compute Standard Deviation
 * Email: noostroukhov@student.stcc.edu
 * Computes standard deviation of a file
 */

package hw8;

import java.io.IOException;
import java.net.URL;
import java.util.Scanner;

public class ComputeDeviation {
	final static String TITLE = "Niko's Standard Deviation Calculator";
	final static String CONTINUE_PROMPT = "\nPerform another calculation? [y/N] ";

	// **********************************************

	private static double power(double x, int exp) {
		double result = 1.0;

		for (int i = 1; i <= exp; i++)
			result *= x;

		return result;
	}

	private static double deviation(double[] x) {
		double result = 0.0;

		for (int i = 0; i < x.length; i++)
			result += power(x[i] - mean(x), 2);

		result /= x.length - 1;
		return result = Math.sqrt(result);
	}

	private static double mean(double[] x) {
		double result = 0.0;

		for (int i = 0; i < x.length; i++)
			result += x[i];

		return result /= x.length;
	}

	private static double[] populateArray(Scanner sc) {
		int count = sc.nextInt();
		double[] result = new double[count];

		for (int i = 0; i < count; i++)
			result[i] = sc.nextDouble();

		return result;
	}

	// **********************************************

	private static void process(Scanner sc, String args[]) throws IOException {
		System.out.print("Enter filename: ");
		URL url = new URL("https://cs.stcc.edu/~silvestri/csc111/" + sc.nextLine());
		Scanner scanURL = new Scanner(url.openStream());

		double[] arr = populateArray(scanURL);
		double mean = mean(arr);
		double deviation = deviation(arr);

		System.out.printf("Mean: \t\t%.3f\nDeviation: \t%.3f", mean, deviation);

		scanURL.close();
	}

	// **********************************************

	private static boolean doThisAgain(Scanner sc, String prompt) {
		System.out.print(prompt);
		String doOver = sc.nextLine();
		return doOver.trim().equalsIgnoreCase("Y");
	}

	// **********************************************

	public static void main(String args[]) throws IOException {
		System.out.println("Welcome to " + TITLE);
		Scanner sc = new Scanner(System.in);
		do {
			process(sc, args);
		} while (doThisAgain(sc, CONTINUE_PROMPT));
		sc.close();
		System.out.println("Thank you for using " + TITLE);
	}

}