Thread: Can anyone explain this code to me? Calculation of mean and variance.

public class MeanVariance {
    public static void main (String[] args) {
	int len       = args.length;
	double[] data = new double[len];
	double mean, sum = 0, sum2 = 0, var;
 
	for (int i = 0; i < len; i++) {
	    data[i] = Double.parseDouble(args[i]);
	}
 
	for (int i = 0; i < len; i++) {
	    sum += data[i];
	} 
	mean = sum / len;
	System.out.println(mean);
 
	for (int i = 0; i < len; i++) {
	    sum2 += Math.pow((data[i] - mean),2);
	}
	var = sum2 / len;
	System.out.println(var);
   }
}

I really don't understand this code which is used to calculate the mean and variance from a data set.

Yes, i've looked up into that and the code is supposed to calculate the mean and variance and print it out on two separate lines. The mean of N data items is calculated by adding up all the items and dividing the total by N. Variance is defined as the average of the squared distance between each item and the mean. I have problems understanding arrays so it would really help if you explain the code from scratch.

double mean, sum = 0, sum2 = 0, var;

What does the above line mean?