// Survey data analysis with arrays;
// computing the mean, median and mode of the data.
#include <stdio.h>
#define SIZE 99
// function prototypes
void mean( const unsigned int answer[] );
void median( unsigned int answer[] );
void mode( unsigned int freq[], const unsigned int answer[] ) ;
void bubbleSort( unsigned int a[] );
void printArray( const unsigned int a[] );
// function main begins program execution
int main( void )
{
unsigned int frequency[ 10 ] = { 0 }; // initialize array frequency
// initialize array response
unsigned int response[ SIZE ] =
{ 6, 7, 8, 9, 8, 7, 8, 9, 8, 9,
7, 8, 9, 5, 9, 8, 7, 8, 7, 8,
6, 7, 8, 9, 3, 9, 8, 7, 8, 7,
7, 8, 9, 8, 9, 8, 9, 7, 8, 9,
6, 7, 8, 7, 8, 7, 9, 8, 9, 2,
7, 8, 9, 8, 9, 8, 9, 7, 5, 3,
5, 6, 7, 2, 5, 3, 9, 4, 6, 4,
7, 8, 9, 6, 8, 7, 8, 9, 7, 8,
7, 4, 4, 2, 5, 3, 8, 7, 5, 6,
4, 5, 6, 1, 6, 5, 7, 8, 7 };
// process responses
mean( response );
median( response );
mode( frequency, response );
} // end main
// calculate average of all response values
void mean( const unsigned int answer[] )
{
size_t j; // counter for totaling array elements
unsigned int total = 0; // variable to hold sum of array elements
printf( "%s\n%s\n%s\n", "********", " Mean", "********" );
// total response values
for ( j = 0; j < SIZE; ++j ) {
total += answer[ j ];
} // end for
printf( "The mean is the average value of the data\n"
"items. The mean is equal to the total of\n"
"all the data items divided by the number\n"
"of data items ( %u ). The mean value for\n"
"this run is: %u / %u = %.4f\n\n",
SIZE, total, SIZE, ( double ) total / SIZE );
} // end function mean
// sort array and determine median element's value
void median( unsigned int answer[] )
{
printf( "\n%s\n%s\n%s\n%s",
"********", " Median", "********",
"The unsorted array of responses is" );
printArray( answer ); // output unsorted array
bubbleSort( answer ); // sort array
printf( "%s", "\n\nThe sorted array is" );
printArray( answer ); // output sorted array
// display median element
printf( "\n\nThe median is element %u of\n"
"the sorted %u element array.\n"
"For this run the median is %u\n\n",
SIZE / 2, SIZE, answer[ SIZE / 2 ] );
} // end function median
// determine most frequent response
void mode( unsigned int freq[], const unsigned int answer[] )
{
size_t rating; // counter for accessing elements 1-9 of array freq
size_t j; // counter for summarizing elements 0-98 of array answer
unsigned int h; // counter for diplaying histograms freq array values
unsigned int largest = 0; // represents largest frequency
unsigned int modeValue = 0; // represents most frequent response
printf( "\n%s\n%s\n%s\n",
"********", " Mode", "********" );
// initialize frequencies to 0
for ( rating = 1; rating <= 9; ++rating ) {
freq[ rating ] = 0;
} // end for
// summarize frequencies
for ( j = 0; j < SIZE; ++j ) {
++freq[ answer[ j ] ];
} // end for
// output headers for result columns
printf( "%s%11s%19s\n\n%54s\n%54s\n\n",
"Response", "Frequency", "Histogram",
"1 1 2 2", "5 0 5 0 5" );
// output results
for ( rating = 1; rating <= 9; ++rating ) {
printf( "%8u%11u ", rating, freq[ rating ] );
// keep track of mode value and largest frequency value
if ( freq[ rating ] > largest ) {
largest = freq[ rating ];
modeValue = rating;
} // end if
// output histogram bar representing frequency value
for ( h = 1; h <= freq[ rating ]; ++h ) {
printf( "%s", "*" );
} // end inner for
puts( "" ); // being new line of output
} // end outer for
// display the mode value
printf( "\nThe mode is the most frequent value.\n"
"For this run the mode is %u which occurred"
" %u times.\n", modeValue, largest );
} // end function mode
// function that sorts an array with bubble sort algorithm
void bubbleSort( unsigned int a[] )
{
unsigned int pass; // pass counter
size_t j; // comparison counter
unsigned int hold; // temporary location used to swap elements
// loop to control number of passes
for ( pass = 1; pass < SIZE; ++pass ) {
// loop to control number of comparisons per pass
for ( j = 0; j < SIZE - 1; ++j ) {
// swap elements if out of order
if ( a[ j ] > a[ j + 1 ] ) {
hold = a[ j ];
a[ j ] = a[ j + 1 ];
a[ j + 1 ] = hold;
} // end if
} // end inner for
} // end outer for
} // end function bubbleSort
// output array contents (20 values per row)
void printArray( const unsigned int a[] )
{
size_t j; // counter
// output array contents
for ( j = 0; j < SIZE; ++j ) {
if ( j % 20 == 0 ) { // begin new line every 20 values
puts( "" );
} // end if
printf( "%2u", a[ j ] );
} // end for
} // end function printArray
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