Not Printing Average - c

Question

I have a project going in two files, but I cannot get the main program to print out the average variable, I just get 0.0 no matter what I change. It also does not print out a whole other function Any Tips?
Main File:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
float average(void);
float std_dev(float);
float output(float);
float array[10] = {4.8, 12.98, 82.1, 5.98, 19.75, 24.9, 75.7, 3.45, 10.0, 28.11};
extern float avg;
int main()
{
float s = 0.0;
printf("The average value of the array is %.2f \n", avg);
s = std_dev(avg);
printf("The standard deviation of the array is %.2f \n", s);
return 0;
}
static void output(float var)
{
printf("The value of the variable is %.2f \n", var);
}
Second File:
#include <math.h>
extern float array[];
float avg = 26.78;
static float average()
{
int n;
float sum = 0.0, mean=0.0;
for(n=0; n<10; n++)
sum = sum + array[n];
mean= sum/10;
output(mean);
return mean;
}
float std_dev()
{
int n;
float cumm_diff = 0.0;
for(n=0; n<10; n++)
cumm_diff += (avg -array[n]) * (avg -array[n]);
return sqrt(cumm_diff/10);
}

Answer 1

the following proposed code:
cleanly compiles
performs the desired functionality
demonstrates how to execute functions in external files
properly prototypes the functions
removes extraneous code
properly formats the code for ease of readability and understanding
eliminates the 'magic' numbers
lets the compiler determine how many items are in the array
uses float literals rather than double literals
documented why each of the system header files is included
used meaningful parameter and variable names
derived the value of count at compile time
cast the int count parameter, when needed, to a float
and now the proposed code:
header file: main.h
#ifndef MAIN_H
#define MAIN_H
void output(float var);
extern float avg;
#endif // MAIN_H
header file: util.h
#ifndef UTIL_H
#define UTIL_H
float calc_std_dev( float *, int );
void calc_mean( float *, int );
#endif // UTIL_H
main.c file
#include <stdio.h> // printf()
#include "main.h"
#include "util.h"
float array[] =
{
4.8f, 12.98f, 82.1f, 5.98f, 19.75f,
24.9f, 75.7f, 3.45f, 10.0f, 28.11f
};
int main( void )
{
printf("The average value of the array is %.2f \n", avg);
float s = calc_std_dev( array, sizeof(array)/sizeof(float) );
printf("The standard deviation of the array is %.2f \n", s);
calc_mean( array, sizeof(array)/sizeof(float) );
return 0;
}
void output(float var)
{
printf("The mean value of the array is: %.2f \n", var);
}
util.c file
#include <math.h> //sqrtf()
#include "main.h"
#include "util.h"
float avg = 26.78f;
void calc_mean( float array[], int count )
{
int n;
float sum = 0.0f;
float mean = 0.0f;
for(n=0; n<count; n++)
sum = sum + array[n];
mean= sum/ (float)count;
output(mean);
}
float calc_std_dev( float array[], int count )
{
int n;
float cumm_diff = 0.0f;
for(n=0; n<count; n++)
cumm_diff += (avg -array[n]) * (avg -array[n]);
return sqrtf(cumm_diff / (float)count);
}

Answer 2

You never call your function average(), which is why the average is not computed, but the initialized value avg = 26.78 (not 0 - you probably changed that at some point) is printed and used by std_dev().