C, number defined as int, double in function - c

Question

Input.txt :
1. M 17 160 13.24
2. M 18 177 13.22
3. M 15 162 14.78
4. F 16 169 15.55
5. F 16 161 14.73
6. F 16 160 10.80
7. M 14 192 15.65
8. F 18 197 12.41
I am now having trouble with the function
(this function was given by the teacher)
void calculateAverages(double *dAvHeight, double *dAvAge, double *dAvTime, Student_t *pStudents, int iNumberOfLines);
I can only define dAvHeight dAvAge dAvTime as Ints, however later on i need to change them to float to calculate averages. Can anyone explain how i do that while keep using dAvHeight dAvAge dAvTime.
My question is why can i only define the averages as int if in the function it says double? does the function change the format?
Thanks again
Here is the updated code:
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
int iNumberOfLines = 1;
int dAvHeight = 0, dAvAge = 0, dAvTime = 0;
typedef struct {
int ignore;
char Gender;
int Age;
int Height;
float Time;
} Student_t;
int determineNumberOfLines(FILE *pInputFile);
void readInputData(FILE *pInputFile, int iNumberOfLines, Student_t *pStudents);
void calculateAverages(double *dAvHeight, double *dAvAge, double *dAvTime, Student_t *pStudents, int iNumberOfLines);
// Student_t* searchFastest(Student_t *pStudents, int iNumberOfLines);
// void printToConsole(Student_t *pFastestStudent, double dAvHeight, double dAvAge, double dAvTime);
int main(int argc, char *argv[]) {
FILE *pInputFile = fopen ("resources/Input.txt", "r");
if (pInputFile == NULL){
printf("Fehler beim Öffnen");
return -1;
}
determineNumberOfLines(pInputFile);
//printf("LINES: %d\n",determineNumberOfLines(pInputFile));
Student_t pStudents[iNumberOfLines];
//printf("%d", iNumberOfLines);
readInputData(pInputFile, iNumberOfLines, pStudents);
calculateAverages(dAvHeight, dAvAge, dAvTime, pStudents, iNumberOfLines);
return 0;
}
int determineNumberOfLines(FILE *pInputFile){
fopen ("resources/Input.txt", "r");
int ch;
while(!feof(pInputFile))
{
ch = fgetc(pInputFile);
if(ch == '\n')
{
iNumberOfLines++;
}
}
fclose(pInputFile);
return iNumberOfLines;
}
void readInputData(FILE *pInputFile, int iNumberOfLines, Student_t *pStudents){
fopen ("resources/Input.txt", "r");
int i = 0;
char buffer [120];
while (fgets(buffer, sizeof buffer, pInputFile) != 0)
{
if (sscanf(buffer, "%d. %c %d %d %f", &pStudents[i].ignore, &pStudents[i].Gender, &pStudents[i].Age, &pStudents[i].Height, &pStudents[i].Time) <= sizeof buffer)
{
i++;
}
}
fclose(pInputFile);
}
void calculateAverages(double *dAvHeight, double *dAvAge, double *dAvTime, Student_t *pStudents, int iNumberOfLines){
int i;
int sumHeight = 0;
int sumAge = 0;
float sumTime = 0;
for (i = 0; i <= (iNumberOfLines-1); i++){
sumHeight = sumHeight + pStudents[i].Height;
}
dAvHeight = sumHeight/ iNumberOfLines;
printf("Average Height is = %.2f \n", dAvHeight);
for (i = 0; i<= (iNumberOfLines-1); i++){
sumAge = sumAge + pStudents[i].Age;
}
//dAvAge = sumAge/iNumberOfLines;
printf("Average Age is = %.2f \n", dAvAge);
for (i = 0; i<= (iNumberOfLines-1); i++){
sumTime = sumTime + pStudents[i].Time;
}
//dAvTime = sumTime/iNumberOfLines;
printf("Average Time is = %.2f \n", dAvTime);
}

Answer 1

If you replace:
dAvHeight = sumHeight/ iNumberOfLines;
with this:
*dAvHeight = (double)sumHeight / iNumberOfLines;
Than that should do the trick. You would also have to do something similar to the lines you commented out.
The asterisk is to make sure you are writing to the place where the pointer is pointing and the (double) is in place because otherwise it would first do the division and then the conversion, which could for exmple lead to:
(double)(5 / 2) = (double)2 = 2.0
instead of
(double)5 / 2 = 5.0 / 2 = 2.5

Answer 2

I resolved it by adding
double *dAvHeight;
dAvHeight = malloc(sizeof(dAvHeight));
double *dAvAge;
dAvAge = malloc(sizeof(dAvAge));
double *dAvTime;
dAvTime = malloc(sizeof(dAvTime));
in the main function and removing the int declarations in the start
and by doing what S3gfault suggested
Thanks !