This program calculates the variance from a series of numbers in an array list.
My Code
import java.util.ArrayList;
public class Variance {
// Copy here sum from exercise 63
public static int sum(ArrayList<Integer> list) {
int tot = 0;
for (int num : list) {
tot = tot + num;
}
return tot;
}
// Copy here average from exercise 64
public static double average(ArrayList<Integer> list) {
int tot = 0;
int i = 0;
for (int num : list) {
tot = tot + num;
i++;
}
return (double)tot / i;
}
public static double variance(ArrayList<Integer> list) {
// write code here
double var = 0;
double avg = average(list);
for (double num : list) {
var = var + ((num - avg) * (num - avg));
}
var = var/(list.size() -1);
return var;
}
public static void main(String[] args) {
ArrayList<Integer> list = new ArrayList<Integer>();
list.add(3);
list.add(2);
list.add(7);
list.add(2);
System.out.println("The variance is: " + variance(list));
}
}
Model Code
import java.util.ArrayList;
public class Variance {
// Copy here sum from exercise 63
public static int sum(ArrayList<Integer> list) {
int sum = 0;
for (int number : list) {
sum = sum + number;
}
return sum;
}
// Copy here average from exercise 64
public static double average(ArrayList<Integer> list) {
double sum = (double) sum(list);
return sum / list.size();
}
public static double variance(ArrayList<Integer> list) {
// write code here
double aver = average(list);
double var = 0;
for (int number : list) {
double difference = number - aver;
double squareOfDifference = difference * difference;
var = var + squareOfDifference;
}
var = var / (list.size() - 1);
return var;
}
public static void main(String[] args) {
ArrayList<Integer> list = new ArrayList<Integer>();
list.add(3);
list.add(2);
list.add(7);
list.add(2);
System.out.println("The variance is: " + variance(list));
}
}
Comments
Not that happy with this one. It works but isn’t as well done as the model solution and took way to long to do.