Calculates 1 variable statistics source code

This snippet submitted by Paul Kennedy on 2005-11-21. It has been viewed 11183 times.
Rating of 4.7 with 81 votes
#include <iostream.h>
#include <math.h>

double x_avg(double *x, int n);  // Calculates Average of x array
double sum_x(double *x, int n); // Calculates sum of x array
double sum_x_squared(double *x, int n);  // Calculates the sum of the squares of each element
double sample(double *x, int n);  // Calculates sample stanard deviation
double stan_dev(double *x, int n);  // Calculates standard deviation
int number(int n);  // Returns array size
double xmin(double *x, int n);  // Returns smallest x value
double xmax(double *x, int n);  // Returns largest x value

int main()
{
  unsigned int n;

  cout << "Enter amount of x value:";
  cin >> n;

  double x[n];

  for (int i = 0; i < n; i++)
  {
    cout << "Enter value for x[" << i << "]:";
    cin >> x[i];
  }

  cout << "Mean of x[i]:\t\t\t" << x_avg(x, n) << endl;
  cout << "Sum of x[i]:\t\t\t" << sum_x(x, n) << endl;
  cout << "Sum of x[i] squared:\t\t" << sum_x_squared(x, n) << endl;
  cout << "Sample Standard Deviation:\t" << sample(x, n) << endl;
  cout << "Standard Deviation:\t\t" << stan_dev(x, n) << endl;
  cout << "Number of x values:\t\t" << number(n) << endl;
  cout << "Minimum value of x:\t\t" << xmin(x, n) << endl;
  cout << "Maximum value of x:\t\t" << xmax(x, n) << endl;

  return 0;
}

double x_avg(double x[], int n)
{
  return (sum_x(x, n)/n);
}

double sum_x(double x[], int n)
{
  double sum;

  for (int i = 0; i < n; i++)
  {
    sum += x[i];
  }

  return sum;
}

double sum_x_squared(double x[], int n)
{
  double sum_x_2;

  for (int i = 0; i < n; i++)
  {
    sum_x_2 += pow(x[i], 2);
  }

  return sum_x_2;
}

double sample(double x[], int n)
{
  double sample_stan_dev, sum_xi_x_2;

  for (int i = 0; i < n; i++)
  {
    sum_xi_x_2 += pow(x[i] - x_avg(x, n), 2);
  }

  sample_stan_dev = sqrt(1/((double)n-1) * sum_xi_x_2);

  return sample_stan_dev;
}

double stan_dev(double x[], int n)
{
  double stan_deviation, sum_xi_x_2;

  for (int i = 0; i < n; i++)
  {
    sum_xi_x_2 += pow(x[i] - x_avg(x, n), 2);
  }

  stan_deviation = sqrt(sum_xi_x_2 / n);

  return stan_deviation;
}

int number(int n)
{
  return n;
}

double xmin(double x[], int n)
{
  double minx = x[0];

  for (int i = 0; i < n; i++)
  {
    if (x[i] < minx)
      minx = x[i];
  }

  return minx;
}

double xmax(double x[], int n)
{
  double maxx = x[0];

  for (int i = 0; i < n; i++)
  {
    if (x[i] > maxx)
      maxx = x[i];
  }

  return maxx;
}
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