Thread: Decimal problems

In the latest incarnation of my program, I'm calculating the mean and median (among other information) of a set of numbers, which are being read from a file. My problem is that the mean and the median won't output as decimals. I have them set as doubles and to show the first decimal place, but instead, a 0 is inserted where the number should be. For example, my list of numbers is: 25, 61, 65, 72, 82, 98. While my median should be 68.5, it is displayed as 68.0 My mean should be 67.2 but is displayed as 67.0. Here is my code:

Code:

#include<iostream.h>
#include<iomanip.h>
#include<fstream.h>

void program_description();
void get_info_from_file( ifstream &i_file, int arr[], int &no_items );
void display_array( int arr[], int no_items );
void sort_ascending( int arr[], int no_items );
int get_total( int arr[], int no_items );
int calc_range( int arr[], int no_items );
double calc_mean( int sum, int no_items );
double calc_median( int arr[], int no_items );

const int max_list = 50;

int main()
{
	//Variable Declarations
	int no_values;
	int total;
	int array[max_list];
	ifstream in_file;

	no_values = 0;

	program_description();

	get_info_from_file( in_file, array, no_values );

	display_array( array, no_values );

	sort_ascending( array, no_values );

	get_total( array, no_values );

	total = get_total( array, no_values );

	calc_range( array, no_values );

	calc_mean( total, no_values );

	calc_median( array, no_values );

	return 0;
}

//Function Definitions

void program_description()
/*========================================================================
This function outputs a description of the program to the user.
	INPUT: None
	OUTPUT: None
========================================================================*/
{
	cout << "Greetings!  This program is designed to take the ";
	cout << "data currently stored in\nanother file and display it to you.  It will then ";
	cout << "sort the data, number it,\nand calculate the sum, range, mean, and median.  ";
	cout << "From there a histogram\nof the data is displayed.\n\n";
}

void get_info_from_file( ifstream &i_file, int arr[], int &no_items )
/*========================================================================
This function opens the input stream, gets the data from the file one item at a time, and 
stores each item in an array element.  It also counts the number of items in the file.  
Lastly, the input stream is closed.
	INPUT: A parameter of type ifstream, an array of integers, an integer which
			represents the number of items in the file.
	OUTPUT: This function returns nothing.
========================================================================*/
{
	int data;
	no_items = 0;

	i_file.open("stat_data");
	i_file >> data;
	arr[no_items] = data;
	no_items ++;
	
	
	while ( ! i_file.eof() )
	{
		i_file >> data;
		
		if ( ! i_file.eof() )
		{
			arr[no_items] = data;
			no_items ++;
		}
	}

	i_file.close();

	cout << "The number of items in this array is: " << no_items;
	cout << endl << endl;

	cout << "The array is:\n\n";

	
}

void display_array( int arr[], int no_items )
/*========================================================================
The function traverses the array of integers, outputting each element in the array.
	INPUT: an array of integers, an integer which represents the number of items in
			the file.
	OUTPUT: This function returns nothing.
========================================================================*/
{
	for ( int i = 0; i < no_items; i++ )
	{
		cout << arr[i] << " ";
	}

	cout << endl << endl;
}

void sort_ascending( int arr[], int no_items )
/*========================================================================
This function sorts an array of integers in ascending order using a selection sort.
	INPUT: an array of integers, an integer which represents the number of items.
	OUPUT: This function returns nothing.
========================================================================*/
{
	int i, hold;

	cout << "This is the array sorted in ascending order: " << endl << endl;
	
	for ( int pass = 0; pass < no_items - 1; pass++ )

		for ( i = 0; i < no_items - 1; i++ )

			if (arr[i] > arr[i + 1] )
			{
				hold = arr[i];
				arr[i] = arr[i +1];
				arr[i+1] = hold;
			}

	for ( i = 0; i < no_items; i++ )
		cout << arr[i] << " ";
		cout << endl;

	cout << endl << endl;

}

int get_total( int arr[], int no_items )
/*========================================================================
This function traverses the array of integers and totals the elements in the array.
	INPUT: an array of integers, an integer which represents the number of items 
			in the file
	OUPUT: This function returns an integer which represents the total of all of
			the elements.
========================================================================*/
{
	int sum;

	sum = 0;

	for ( int i = 0; i < no_items; i++ )
	{
		sum = arr[i]+sum;
	}

	cout << "The sum of all the data is: " << sum << endl << endl;

	return sum;
}

int calc_range( int arr[], int no_items )
/*========================================================================
This function calculates the range of the values (highest value - lowest value) for
an array of integers.  It is assumed that the list has already been sorted.
	INPUT: an array of integers, an integer which represents the number of items.
	OUTPUT: This function returns an integers which reprsents the range.
========================================================================*/
{
	int range;

	range = arr[no_items - 1] - arr[0];
	
	cout << "The range of the data is: " << range << endl << endl;

	return range;
}

double calc_mean( int sum, int no_items )
/*========================================================================
This function calculates the mean (arthimetic average) given the total of the elements
and the number of items.
	INPUT: an integer that represents a sum total, an integer which represents the
			number of items
	OUTPUT: this function returns a double that represents the mean
========================================================================*/
{
	double mean;

	cout << setiosflags (ios:: fixed);
	cout << setiosflags (ios:: showpoint);
	cout << setprecision(1);

	mean = sum / (no_items);

	cout << "The mean of the data is: " << mean;
	cout << endl << endl;

	return mean;
}

double calc_median( int arr[], int no_items )
/*========================================================================
This function calculates the media (middle score) of a set of numbers.  It is assumed
that the list has already been sorted.
	INPUT: an array of integers, an integer which represents the number of items
	OUTPUT: this function returns an integer which represents the median
========================================================================*/
{
	int median;
	double median_average;
	int median_1;
	int median_2;
	int no_scores;

	cout << setiosflags (ios:: fixed);
	cout << setiosflags (ios:: showpoint);
	cout << setprecision(1);
	
	no_scores = no_items;

	no_scores = no_scores % 2;

	if ( no_scores == 0 )
	{
		cout << setiosflags (ios:: fixed);
		cout << setiosflags (ios:: showpoint);
		cout << setprecision(1);
		
		median_1 = arr[(no_items / 2) - 1];
		median_2 = arr[no_items / 2];

		median_average = (median_1 + median_2) / 2;

		cout << "There is an even number of items. " << endl;
		cout << "The median of the data is: " << median_average << endl << endl;
	}

	else
	{

		median = arr[no_items / 2];
		
		cout << "There is an even odd of items." << endl;
		cout << "The median of the data is: " << median << endl << endl;

	}

	return median;
}

An integer divided by an integer will result in an integer. So, te solution is..

Code:

mean = static_cast<double>(sum) / (no_items);

Thanks. I had never seen "static_cast<double>" before, but it did the trick. While I never would have figured out what was wrong with the mean, the median was my own fault, in leaving median_1 and median_1 as integers. All I had to do was change the code in my median function to:

Code:

	int median;
	double median_average;
	double median_1;
	double median_2;
	int no_scores;