Quick array fix

This code doesn't seem to be looping properly because it doesn't store the correct array values (in fact, the values are all set to 0 in the end). And I can't figure out why for the life of me..

Code:

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for(i=0; i<min_in_trip/5; i++) {
    for(j=0; j<300; j++)
      fscanf(ifp, "%f%f", &temp, &temp2);
      numrevs += temp;
      gas += temp2;
    if(j == 300)
      array[i] = findfueleff(radius, numrevs, gas);
  }

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I really need this to work so that I can finish working on another program for homework that requires that the program that this code was derived from to work.

Thanks!

P.S. I have attached the .txt file that this program uses.

We like indentation here, but this is not Python, and indentation is no substitute for getting the braces right:

Code:

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for(i=0; i<min_in_trip/5; i++) {
    for(j=0; j<300; j++) {
      fscanf(ifp, "%f%f", &temp, &temp2);
      numrevs += temp;
      gas += temp2;
    }
    if(j == 300)
      array[i] = findfueleff(radius, numrevs, gas);
  }

---

(1)

Code:

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>    for(j=0; j<300; j++)
>      fscanf(ifp, "&#37;f%f", &temp, &temp2);
>      numrevs += temp;
>      gas += temp2;

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Assuming you want to sum all 300 items, you're missing some braces:

Code:

---

    for(j=0; j<300; j++)
    {
      fscanf(ifp, "%f%f", &temp, &temp2);
      numrevs += temp;
      gas += temp2;
    }

---

(2) Make sure temp and temp2 are declared as floats versus doubles, as %f is for reading floats. Use %lf to read doubles instead.

(3) You should probably check the return of fscanf() to be sure it actually read two floats:

Code:

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      if (fscanf(ifp, "%f%f", &temp, &temp2) == 2)
      {
        /* Sum data */
      }
      else
      {
        /* Data not read */
      }

---

Code:

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/* Definition libraries. */
#include <stdio.h>
#include <stdlib.h>

/* Defines constants. */
#define PI 3.14159
#define INCHES_IN_FEET 12
#define FEET_IN_MILE 5280

/* Initializes functions. */
double findfueleff(double radius, double numrevs, double gas);
void printGraph(double array[], int length);

int main() {
 
  /* Defines variables. */
  FILE *ifp;
  int i, j;
  int min_in_trip, radius;
  double array[6], temp, temp2, numrevs, gas;
  char filename[20];
 
  /* Checks and opens input file. */
  do {
    printf("Enter the name of the file storing tire gas and tire rotation data.\n");
    scanf("%s", &filename);
    ifp = fopen(filename, "r");
 
    if(ifp == NULL)
      printf("File not found.\n");
  }
  while(ifp == NULL);
  printf("\n");
 
  /* Scans in length of trip and tire radius and determines array length. */
  fscanf(ifp, "%d%d", &min_in_trip, &radius);
 
  /* Scans in values from file. */
  for(i=0; i<min_in_trip/5; i++) {
    for(j=0; j<300; j++) {
      fscanf(ifp, "%lf%lf", &temp, &temp2);
      numrevs += temp;
      gas += temp2;
    }
    if(j == 300)
      array[i] = findfueleff(radius, numrevs, gas);
  }
   
  /* Prints out bar graph to display data. */
  printGraph(array, min_in_trip/5);
 
  /* Closes input file. */
  close(ifp);
 
  system("PAUSE");
  return (0);

}

/* Checks values that calculate fuel efficiency and returns the respective value. */
double findfueleff(double radius, double numrevs, double gas) {
  if(numrevs == 0 && gas > 0)
    return 100;
  else if(numrevs == 0 && gas == 0) {
    return 0;
  }
  else
    return ((2*PI*radius/INCHES_IN_FEET/FEET_IN_MILE)*numrevs)/gas;
}

/* Creates bar graph. */
void printGraph(double array[], int length) {

  int i, j;
 
  for(i=95; i>=0; i=i-5) {
    printf("%-4d", i);
    for(j=0; j<length; j++) {
      if(array[j]>=i)
        printf("***** ");
      else
        printf("      ");
    }
    printf("\n");
  }

  printf("    ");
  for(i=0; i<=34; i++) {
    printf("-");
  }
  printf("\n");
  printf("    ");
  printf("00-05 05-10 10-15 15-20 20-25 25-30\n");
  printf("\n");
}

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Still not working with the above attached text file, so I decide to post the entire program instead.

It would probably be a good idea to initialize numrevs and gas.

double array[6], temp, temp2, numrevs, gas; ..?

..unless there is something else I need to do.

I never said you hadn't declared them, I said you hadn't initialized them. Print the value of numrevs before the for-loop and see what you see.

I just understood what you meant, and I set both variables equal to 0.

But I'm not sure if it is printing the correct information still..

In your code, when would this ever not be true:

Code:

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    if(j == 300)

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So what is the point in it?