EASY Function: Array Average

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  1. #1
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    EASY Function: Array Average

    What is an example of a function I would use to find the average value if I have an array of known size?

    i.e.

    Code:
    const int LENGTH = 5;
    double a[LENGTH] = {1,5,6,8,10};
    double avg;
    double sum;
    any ideas? I know this is probably super easy...

    thanks

  2. #2
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    How would you do the calculation if you were doing it by hand?

    Generally, the same method that you'd use by hand works on computer. In this case, you'd add the numbers together and divide by the number of "samples" (elements in the array).

    --
    Mats

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    Yea, i can do it by hand easily...what I don't understand is how to add each element to the next one. If you can help me with that I would really appreciate it. Here's what I have:
    Code:
    double avg = 0;
    	for(int i=0; i<npts; i++)
    		avg = (avg + a[i])/5;
    	return avg;
    is this even close?

  4. #4
    and the hat of int overfl Salem's Avatar
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    Would you divide by 5 each time if you were doing it by hand?

    Or would you only divide the total at the end just the once?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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    I figured out how to do the avg:
    Code:
    int main()
    {
    	const int SIZE = 5; //max array size
    	double x[SIZE] = {1,5,6,8,10};
    	int num_points = 0;
    
    	double sum = 0;
    	double avg;
    	for(int i=0;i<SIZE;i++)
    	{
    	sum = sum + x[num_points];
    	num_points++;
    
    	}
    	avg = sum/SIZE;
    	cout<<"the average of the values in the array is:"<<endl;
    	cout<<avg<<endl;
    	//for(int i=0; i<SIZE; i++)
    	//{
    	return 0;
    }
    now the problem gets even more fun

    thanks for the help

  6. #6
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    Quote Originally Posted by benjamin923 View Post
    I figured out how to do the avg:
    Code:
    int main()
    {
    	const int SIZE = 5; //max array size
    	double x[SIZE] = {1,5,6,8,10};
    	int num_points = 0;
    
    	double sum = 0;
    	double avg;
    	for(int i=0;i<SIZE;i++)
    	{
    	sum = sum + x[num_points];  /* delete this line, num_points is an unneeded variable, just use i */
                /* indenting inside curly braces is a BIG help for us poor humans - please do it */
                sum += x[i];   /* this is C standard idiom, learn it well */
    	num_points++;  /* delete this line */
    
    	}
    	avg = sum/SIZE;
    	cout<<"the average of the values in the array is:"<<endl;
    	cout<<avg<<endl;
    	//for(int i=0; i<SIZE; i++)
    	//{
    	return 0;
    }
    now the problem gets even more fun

    thanks for the help
    The advice to do your program similarly to how you'd do it by hand, is especially good for beginner's. If you can't do something, it's a rare day indeed that you'll be able to program a computer to do that something.

    If you can do a task by hand, it gives a very fertile soil from the description of exactly how you do it, to let the seed of a program, grow.
    Last edited by Adak; 08-02-2007 at 06:19 PM.

  7. #7
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    Thanks for that advice - anything to save time and space helps a bunch.
    now if i can only figure out the other part....(next post on board) AHHHHH

  8. #8
    Deathray Engineer MacGyver's Avatar
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    Why post C++ code in the C section? At least learn what language you're learning before you start learning it.

  9. #9
    and the hat of int overfl Salem's Avatar
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    Agreed - moved.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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