Question

I’m trying to find the standard deviation of an array using a for loop.
I have some code that might work but it gives me errors.
I would appreciate some guidance and help! 🙂

Here is the code:

double StandardDeviation() {
    double Dog,Variance,StandardDeviationFormula;

    for (int k = 0; k < TheArrayAssingment.length; k++) {

         Dog = Dog + (TheArrayAssingment[k] - Average()) 
                      * (TheArrayAssingment[k] - Average());

         Variance = Dog / (TheArrayAssingment.length - 1);
         StandardDeviationFormula = Math.sqrt(Variance);

    }
    return StandardDeviationFormula;
}

Answer 1

Since you are obviously a beginner at programming in general as well as new to Java, here is some general advice:

1. Always following the coding standards / convention. They are there to make you code more readable for other people. Do it even in little throw-away examples, so that you get into the habit of doing it in the cases where it matters.

2. It is a “universal” convention in Java that method and variable names start with a lower-case letter. You have started them all with an upper-case letter. Change StandardDeviation to standardDeviation, Variance to variance and so on.

3. Choose variable and method names that accurately reflect the intended meaning. For instance:

   • Dog is obviously meaningless.
   • TheArrayAssingment might be meaningful, but I can’t figure it out.
   • StandardDeviationFormula is inaccurate. It doesn’t contain a formula. It contains a value that is the result of applying a formula.

   It also helps if you spell method and variable names correctly …

   (There are exceptions to this. For instance, most seasoned programmers think it is perfectly acceptable to use conventional and abbreviated names for local variables when the meaning is self-evident. For example, ex or e for an exception, i / j / k for a loop variable, it for an iterator object. As you read more of other peoples’ code, you will get to see / understand the “idioms”.)