// CSE1502 Spring 2009 Homework #5 - Matt Mahoney
//
// This program prompts the user to enter the name of a file
// containing a list of 2 or more numbers separated by white space.
// Then it prints the mean, median, range, standard deviation,
// and the list sorted in ascending order.
// If the file does not exist or contains less than 2 numbers, then
// it prints an error message.

#include <iostream>
#include <fstream>
#include <cmath>
#include <cstdlib>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{

  // Open the input file
  string filename;
  cout << "Input file? ";
  cin >> filename;
  ifstream in(filename.c_str());
  if (!in)
  {
    cout << "Error: " << filename << " not found\n";
    exit(1);
  }

  // Read the list of numbers into a vector
  vector<double> v;
  double x;
  while (in >> x)
    v.push_back(x);

  // Make sure the size is at least 2
  int n = int(v.size());
  if (n < 2)
  {
    cout << "Error: input must contain at least 2 numbers\n";
    exit(1);
  }

  // Print the size
  cout << "There are " << n << " numbers\n";

  // Sort the vector
  sort(v.begin(), v.end());

  // Compute the mean
  double mean = 0;
  for (int i=0; i<n; ++i)
    mean += v[i];
  mean /= n;
  cout << "The mean is " << mean << "\n";

  // Compute the median
  double median;
  if (n % 2 == 0)
    median = (v[n/2 - 1] + v[n/2]) / 2;
  else
    median = v[n/2];
  cout << "The median is " << median << "\n";

  // Compute the range
  double range = v[n-1] - v[0];
  cout << "The range is " << range << "\n";

  // Compute the standard deviation
  double sd = 0;
  for (int i=0; i<n; ++i)
    sd += (v[i] - mean) * (v[i] - mean);
  sd = sqrt(sd / (n-1));
  cout << "The standard deviation is " << sd << "\n";

  // Print the list in order
  cout << "The list in order is";
  for (int i=0; i<n; ++i)
    cout << " " << v[i];
  cout << "\n";

  return 0;
}