Program Always Returning Zero

[ldelsignore]

This program is giving me a major headache, while it should be very simple. It will only return 0 each time I run it. I have pulled the program apart and run each function separately in a driver program. Each function appears to work fine on its own, however for some confounding reason, it invariably returns the value of zero each time I run the program as a whole. I thank anyone in advance for pointing out what I must surly be missing.

#include <iostream>
#include <cmath>
void deviation(double& ave2);
void average(double& first, double& second, double& third, double& fourth, double& ave1);
void average2(double& first, double& second, double& third, double& fourth, double& ave1, double& ave2);
using namespace std;
int main()
{
    double first, second, third, fourth;
    double ave1, ave2;
    cout << "Enter four numbers." << endl;
    cin >> first;
    cin >> second;
    cin >> third;
    cin >> fourth;
    average(first, second, third, fourth, ave1);
    average2(first, second, third, fourth, ave1, ave2);
    deviation(ave2);
    cout << ave2;
    return 0;
}

void average(double& first, double& second, double& third, double& fourth, double& ave1)
{
    ave1 = (first + second + third + fourth) / 4;
}

void average2(double& first, double& second, double& third, double& fourth, double& ave1, double& ave2)
{
    ave2 = (first - ave1) + (second - ave1) + (third - ave1) + (fourth - ave1);
}

void deviation(double& ave2)
{
    cout << "The standard deviation of this set is " << sqrt(ave2) << ".";
}

[Mats]

void functions return nothing. You want them to return ave1, so they should be double functionname and should end with returning average.

[ldelsignore]

That doesn't seem to change anything. The program still returns 0. Also, I learned in class that one can in fact put cout in a void function, and it would work perfectly fine. It is in the book examples. Here is my revised (but still non-functioning) code.

#include <iostream>
#include <cmath>
double deviation(double& ave2);
void average(double& first, double& second, double& third, double& fourth, double& ave1);
void average2(double& first, double& second, double& third, double& fourth, double& ave1, double& ave2);
using namespace std;
int main()
{
    double first, second, third, fourth;
    double ave1, ave2;
    cout << "Enter four numbers." << endl;
    cin >> first;
    cin >> second;
    cin >> third;
    cin >> fourth;
    average(first, second, third, fourth, ave1);
    average2(first, second, third, fourth, ave1, ave2);
    cout << "The standard deviation is " << deviation(ave2);
    return 0;
}

void average(double& first, double& second, double& third, double& fourth, double& ave1)
{
    ave1 = (first + second + third + fourth) / 4;
}

void average2(double& first, double& second, double& third, double& fourth, double& ave1, double& ave2)
{
    ave2 = (first - ave1) + (second - ave1) + (third - ave1) + (fourth - ave1);
}

double deviation(double& ave2)
{
    return sqrt(ave2);
}

[Garion]

I tried simplifying the program down some and it seems to work. Somethign got broke when you added more in.

or wait.. hmm.. I never changed the divided by 4. when i change it to divided by 2 it goes back to zero.

hmmm

#include <iostream>
#include <cmath>
void deviation(double& ave2);
void average(double& first, double& second, double& ave1);
void average2(double& first, double& second, double& ave1, double& ave2);
using namespace std;
int main()
{
    double first, second;
    double ave1, ave2;
    cout << "Enter two numbers." << endl;
    cin >> first;
    cin >> second;
    average(first, second, ave1);
    average2(first, second, ave1, ave2);
    deviation(ave2);
    cout << ave2;
    return 0;
}

void average(double& first, double& second, double& ave1)
{
    ave1 = (first + second) / 4;
}

void average2(double& first, double& second, double& ave1, double& ave2)
{
    ave2 = (first - ave1) + (second - ave1);
}

void deviation(double& ave2)
{
    cout << "The standard deviation of this set is " << sqrt(ave2) << ".";
}

[ldelsignore]

What compiler are you using? Because when I change the / 4 in the average function to / 2 to comply with the fact that there would be two numbers, it goes back to 0. I am starting to think that there must be something wrong with my complier. It seems that when a simple program should be perfectly correct, it either won't compile or won't compile properly.

[Garion]

Try writing it out by hand without code. I think the way you have it written will always return zero.

I mean you have

ave2 = (first - ave1) + (second - ave1);

try to fill in some values on that

say we input 2 and 4 making the average 3


(2 - 3) + (4 - 3 ) = 0


lets say we had 3 values using your code above


say we input 2, 4, and 6 making the average 4

(2 - 4) + (4 - 4) + ( 6 - 4) = 0


You are doomed to always have it at zero with the way it's written. The program is functioning fine. Just that formula you have written is wrong some how.


I tried googling standard deviation and I found this on wikipedia.

http://en.wikipedia.org/wiki/Standard_deviation


so using the 2, 4, 6 example with an average of 4

it should be

(2-4)squared + (4 - 4 ) squared + (6-4) squared giving you a result of 8

then the standard deviation would be the square root of (8 / 3)

at least I think thats how it should function

basically std deviation would = square root of (the sum of the square of the elements deviations divided by the number of elements)

not sure how to write that in mathy form.

[ldelsignore]

I think you are right. I have adjusted the formula, and the program finally seems to be outputting sensible information. Thank you.

[Garion]

I think it should look like this. for standard deviation.

I doubled checked with a calculator. I probably should get a better one lol.

This works fine. You should be able to extend this to as many as you need.

oh, and if anybody knows how to express "squared" in c++ please educate me :)

#include <iostream>
#include <cmath>
void deviation(double& step2_result);
void average(double& first, double& second, double& third, double& ave1);
void step2(double& first, double& second, double& third, double& ave1, double& step2_result);
using namespace std;
int main()
{
    double first, second, third;
    double ave1,step2_result;
    cout << "Enter three numbers." << endl;
    cin >> first;
    cin >> second;
    cin >> third;
    average(first, second, third, ave1);
    step2(first, second, third, ave1, step2_result);
    deviation(step2_result);
    cout << step2_result;
    return 0;
}

void average(double& first, double& second, double& third, double& ave1)
{
    ave1 = (first + second + third) / 3;
    cout << ave1 << "\n";
}

void step2(double& first, double& second, double& third, double& ave1, double& step2_result)
{
    step2_result = ((first - ave1)*(first - ave1)) + ((second - ave1)*(second - ave1)) + ((third - ave1)*(third - ave1)); //adds up the value of deviation squared for each input
}

void deviation(double& step2_result)
{
    cout << "The standard deviation of this set is " << sqrt(step2_result/3) << "."; //make sure to divide by the number of inputs
}

[ldelsignore]

Yeah, that's essentially what I did. Thanks.

[giblit]

You guys are both doing integer division for a double...

 ave1 = (first + second + third + fourth) / 4;
ave1 = (first + second + third) / 3;

10 / 3 = 3
10 / 3.0 = 3.3333

Always either
a) cast to a double/float
B) add '.' or ".0" after the number
c)add ".0f" to end of number

[Catfish666]

d) Add ".f" after the number.

[TheBeardedQuack]

What do you mean by returning 0 as a whole program?
Do you mean that the termination code of the program is always 0? (if so this is just because you've got return 0; at the end of you main function).

Otherwise what is your actual problem?