/*********************
 * Name: Geoff Towell
 * Purpose: functions to compute mean and standard deviation
 * Wrttten: August 5, 2019
 * Modified: Sep 6, 2019
 *           Sep 12, 2019
 *********************/
#include<stdio.h>
#include <math.h>
#include <time.h>
#include<stdlib.h>

/**
 * Get a random number in specified range
 * param min the lower end of the range
 * param max the upper end of the range
 * return the random number 
 */
int randrange(int min, int max)
{
       return min + rand() / (RAND_MAX / (max - min + 1) + 1);
}

/**
 * Compute the mean of an array of integers
 * param n the size of the array
 * param data the array
 * return the mean of the array
 **/
float calculateMean(int n, int data[n])
{
    float sum = 0.0;
    int i;
    for(i=0; i<n; ++i)
    {
        sum += data[i];
    }
    return sum/n;
}

/**
 * Compute the standard deviation of an array of integers
 * param n the size of the array
 * param data the array
 * return the standard deviation of the array
 **/ 
float calculateSD(int n, int data[n])
{
    float mean=calculateMean(n, data), standardDeviation = 0.0;
    int i;
    for(i=0; i<n; ++i)
        standardDeviation += pow((float)(data[i] - mean), 2); 
    return sqrt(standardDeviation/(n-1));
}

int main(void)
{
    srand(time(NULL)); // initialize randomnumber generation.  Using time means each run gets a different random sequence
    int r1[10000];
    int lr1, mr1;
    printf("Range 1: low, high: ");
    scanf("%d %d", &lr1, &mr1);
    for (int i=0; i<10000; i++)
    {
	r1[i]=randrange(lr1, mr1);
    }
    printf("Mean         %10.2f\n", calculateMean(10000, r1));
    printf("Standard Dev %10.2f\n", calculateSD(10000, r1));
}