Help on standard deviation please

Question

I am writing a program to find standard deviation. Below is what I have so far "not much I know" but I have tried so don't get flame happy. It errors out and I have tried to fix it. I know the formula for standard deviaition but I can't seem to program it right. I also need to program the code to have three methods the main, an Average method, and a standard deviation method. I know how to make a method but I am having trouble on how to call them. Any help would be appreciated. I am not asking anyone to do my work for me just give me some tips. I would rather take a 0 on the assignement and learn later than turn in someone else's work becaue I will never pass my final if I do that.
import java.text.*;
import javax.swing.*;
class StandardDeviation{
     public static void main(String [] args){
     DecimalFormat df = new DecimalFormat("0.00");
     //Average Code Segment
          double [] values = {10,20,30,4,2}; //Assigns numbers to values
          double valueAverage,square, sum = 0;
          for(int i = 0; i < values.length; i ++){
               sum += values;
          valueAverage = sum / 5; //Computes Average
          System.out.println("Average is: " +valueAverage); //Displays average of values to test to see if it worked     
//Deviation Code Segment
for (int i = 0; i < values.length; ++i)
double diff = values - valueAverage;
sum+= diff*diff;
System.out.println(+ Math.sqrt(sum/(values.length - 1))); // here I was trying to test to see if my formula worked          
I get the following error
java:20: operator - cannot be applied to double[],double
double diff = values - valueAverage;

Answer 1

Okay this code works. Duffymo can you give me some pointers of writing this code using multiple methods? I can write the methods. I just have a hard time grasping the concept of calling them. I have had a hard time learning this in java. I also looked at some of your past posts on Standard Deviation I see what you are saying about the multiple methods. I know that I need a main method that would probably include the values. Then I would have a average method which would call the values to compute the average. Then I would have the StdDev method to compute the Standard deviation method. Any tips on where to begin on this?
mport java.text.*;
import javax.swing.*;
class StandardDeviation{
     public static void main(String [] args){
     DecimalFormat df = new DecimalFormat("0.00");
     //Average Code Segment
          double [] values = {10,20,30,4,2}; //Assigns numbers to values
          double valueAverage,square, sum = 0;
          for(int i = 0; i < values.length; i ++){
               sum += values;
          valueAverage = sum / 5; //Computes Average
          System.out.println("Average is: " +valueAverage); //Displays average of values     
          //return valueAverage;
     //Deviation Code Segment
for (int i = 0; i < values.length; ++i)
double diff = values[i]- valueAverage;
sum+= diff*diff;
System.out.println("The Standard deviation is: "+ df.format(Math.sqrt(sum/(values.length - 1))));