array_sort.c

// 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[], unsigned const int answer[]);
void bubbleSort(unsigned int a[]);
void printArray(unsigned const 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);
}

// calculate average of all response values
void mean(const unsigned int answer[]) {
	printf_s("%s\n%s\n%s\n", "********", "  Mean", "********");

	unsigned int total = 0; // variable to hold sum of array element

	// total response values
	for (size_t j = 0; j < SIZE; ++j) {
		total += answer[j];
	}
	printf_s("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);
}

// sort array and determine median element's value
void median(unsigned int answer[]) {

	printf_s("\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("%s", "\n\nThe sorted array is");
	printArray(answer); // output sorted array

	// display median element
	printf_s("\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]);
}

// determine the most frequent response
void mode(unsigned int freq[], const unsigned int answer[]) {
	printf_s("\n%s\n%s\n%s\n", "********", "  Mode", "********");

	// initialize frequencies to 0
	for (size_t rating = 1; rating <= 9; ++rating) {
		freq[rating] = 0;
	}

	// summarize frequencies
	for (size_t j = 0; j < SIZE; ++j) {
		++freq[answer[j]];
	}
	// output headers for result columns
	printf_s("%s%11s%19s\n\n%54s%54s\n\n",
		"Response", "Frequency", "Histogram",
		"1   1   2   2", "5   0   5   0   5");

	// output results
	unsigned int largest = 0; // response largest frequency 
	unsigned int modeValue = 0; // response most frequent response

	for (size_t rating = 1; rating <= 9; ++rating) {
		printf_s("%8u%11u          ", rating, freq[rating]);

		// keep track of mode value and largest frequency value
		if (freq[rating] > largest) {
			largest = freq[rating];
			modeValue = rating;
		}
		// output histogram bar representing frequency value
		for (unsigned int h = 1; h <= freq[rating]; ++h) {
			printf_s("%s", "*");
		}
		puts(""); // begin new line of output
	}
	// display the mode value
	printf_s("\nThe mode is the most frequent value.\n"
		"For this run the mode is %u which occurred"
		" %u times.\n", modeValue, largest);
}

// function that sorts an array with bubble sort algorithm
void bubbleSort(unsigned int a[]) {

	// loop to control number of passes
	for (unsigned int pass = 1; pass < SIZE; ++pass) {

		// loop control number of comparisons per pass
		for (size_t j = 0; j < SIZE - 1; ++j) {

			// swap elements if out of order
			if (a[j] > a[j + 1]) {
				unsigned int hold = a[j];
				a[j] = a[j + 1];
				a[j + 1] = hold;
			}
		}
	}
}

//output array contents (20 values per row)
void printArray(const unsigned int a[]) {

	// output array contents
	for (size_t j = 0; j < SIZE; ++j) {

		if (j % 20 == 0) { // begin new line every 20 values
			puts("");
		}
		printf_s("%2u", a[j]);
	}
}