One of my value in array gives "0" - c

Question

In my file includes two columns and I'm try to gather data from file. I need to compare two value in one column. For example, if array[5] is higher than array[4], do something. Here my code:
int control(double col2[], double col3[], int subscript){
double a, b, fcontrol ;
int k /* group */ ;
/* some necessary values for JD controlling */
a = col2[subscript] ;
b = col2[subscript-1] ;
/* for JD controlling */
fcontrol = a - b ;
printf("kontrol = %.12f a = %.12f b = %.12f\n", fcontrol, a, b) ;
/* if value of between two data is equal or higher than 10 hour return 1 */
if(fcontrol >= 0.416666666667){
return 1 ;
}
else{
return 0 ;
}
b is always 0. How can I fix it?
My terminal is :
kontrol = 258.426728989849 a = 258.426728989849 b = 0.000000000000
kontrol = 258.447161800788 a = 258.447161800788 b = 0.000000000000
kontrol = 258.467594711488 a = 258.467594711488 b = 0.000000000000
kontrol = 260.245248070103 a = 260.245248070103 b = 0.000000000000
kontrol = 260.265680861012 a = 260.265680861012 b = 0.000000000000
kontrol = 260.286113551461 a = 260.286113551461 b = 0.000000000000
kontrol = 260.306546441912 a = 260.306546441912 b = 0.000000000000
Here my all code :
/* TASK */
#include<stdio.h>
int kontrol(double col2[], double col3[], int subscript) ;
int main(){
int kolon1,
n = 0, /* for array */
j, z, /* for "for" loopr */
flag = 0 ;
int grup = 0 ;
double kolon2, kolon3,
col2[100000], col3[100000] ;
char ignore[100];
FILE *okuPtr ;
FILE *yazPtr ;
char oku_tbl[100] ;
sprintf(oku_tbl, "deneme.tbl") ;
/* error if file isnt opened*/
if ((okuPtr = fopen(oku_tbl, "r")) == NULL)
printf("%s Acilamadi", oku_tbl) ;
/* file is opened */
else{
char yaz_tbl[100] ;
sprintf(yaz_tbl, "deneme_data.tbl") ;
/* errof if file isnt opened */
if((yazPtr = fopen(yaz_tbl, "w")) == NULL)
printf("%s acilamadi\n", yaz_tbl) ;
/* file is opened */
else{
/* first read */
fscanf(okuPtr, "%d%lf%lf", &kolon1, &kolon2, &kolon3) ;
/* until end of file */
while (!feof(okuPtr)){
/* ignore first 3 line */
fgets(ignore, 100, okuPtr) ;
col2[n] = kolon2 ;
col3[n] = kolon3 ;
flag = control(col2, col3, n) ;
n++ ;
/* if flag == 1 */
if (flag == 1){
for (z = 0 ; z <= --n ; z++){
fprintf(yazPtr, "%d\t%.12f\t%.12f\n", grup, col2[z], col3[z]) ;
}
n = 0 ;
grup++ ;
}
/* yeni veri oku */
fscanf(okuPtr, "%d%lf%lf", &kolon1, &kolon2, &kolon3) ;
}
/* diziyi yazdir
for (j = 0 ; j <= n-1 ; j++){
printf("%d\t%-.12f\t%-.12f\n", k, col2[j], col3[j]) ;
} */
}
}
return 0 ;
}
int control(double col2[], double col3[], int subscript){
double a, b,
fcontrol ;
int k /* group */ ;
/* some necessary values for JD controlling */
a = col2[subscript] ;
b = col2[subscript-1] ;
/* for JD controlling */
fcontrol = a - b ;
printf("kontrol = %.12f a = %.12f b = %.12f\n", fcontrol, a, b) ;
/* if value of between two data is equal or higher than 10 hour return 1 */
if(fcontrol >= 0.416666666667){
return 1 ;
}
else{
return 0 ;
}
}

Answer 1

Problem is that when you call control for first time when n=0
flag = control(col2,col3, n);
But notice here b=col2[subscript-1] will actually be b=col2[-1] which is creating problem as array indexing start with 0 thus your program has this behaviour .
while (!feof(okuPtr))
It is always wrong. See here-Why is “while ( !feof (file) )” always wrong?
Instead use this -
while(fgets(ignore, 100, okuPtr))
{
/*Your code*/
}