reading in data into an array of arrays

Hey,

I have 0 experience in C (although I know R somewhat well and know a little with Perl) and was assigned a completely unreasonable assignment in my R computing class. I'm trying to read in a text file into C as a multidimensional array. The data is 100 rows by 6 columns and contains positive and negative values with decimals (ie -1.24354). I want to store this data in C so that data[0][0] corresponds with the value in the first row and column.

Code:

---


#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>

#define nRow 100
#define nCol 6

int main()
{
        int i,j;
        double data[nRow][nCol];
       
    FILE *fpIn = NULL;
        fpIn = fopen("data.txt", "r");
        if(fpIn == NULL)
        {
                printf("Cannot open file!\n");
                getchar();
                return 1;
        }
        else
        {
                printf("File is now open. Press Enter...\n");
        }
   
    for(i = 0; i < nRow; i++) {
        for(j = 0; j < nCol; j++) {
            fscanf(fpIn, "%d", &data[i][j]);
        }     
    }   
    printf("file has been read in\n");
    printf("the first entry is:\n");
    printf("%d\n", &data[1][0]);
     
    getchar(); 
    fclose(fpIn);               
       
        return 0;       
}

---

The value is supposed to be -1.12, but compiling and running the code returns: 2288848. When I change %d into %s, it reads the correct string, but I want these numbers as doubles. What exactly I am doing wrong?

Thanks in advance!

What you can do read the data from the file descriptor fpIn into an array of chars char*

and then convert it to float, double or int what ever you want


with these functions


atoi()
atof()
atod()

defined in <stdlib.h>

Do you see the problem with this?

Code:

---


        if(fpIn == NULL)  //if the file can't be opened
        {
                printf("Cannot open file!\n");
                getchar();
                return 1;
        }
        else                    //your entire program has to fit inside this else statement,
        {                      //which you don't need at all.
                printf("File is now open. Press Enter...\n");
        }


   
    for(i = 0; i < nRow; i++) {
        for(j = 0; j < nCol; j++) {
            fscanf(fpIn, "%d", &data[i][j]);
        }     
    }

---

You need to start printing up your values from data[0][0], instead of data[1][0], as above.

I'm thinking you missed "return 1;", there, Adak.

And doubles is "%lf".

Quote:

---

Originally Posted by Adak

Do you see the problem with this?

Code:

---


        if(fpIn == NULL)  //if the file can't be opened
        {
                printf("Cannot open file!\n");
                getchar();
                return 1;
        }
        else                    //your entire program has to fit inside this else statement,
        {                      //which you don't need at all.
                printf("File is now open. Press Enter...\n");
        }


   
    for(i = 0; i < nRow; i++) {
        for(j = 0; j < nCol; j++) {
            fscanf(fpIn, "%d", &data[i][j]);
        }     
    }

---

---

Did you read the code carefully the logic is correct dude. See the original code

Code:

---

int main()
{
        int i,j;
        double data[nRow][nCol];
       
    FILE *fpIn = NULL;
        fpIn = fopen("data.txt", "r");
        if(fpIn == NULL)
        {
                printf("Cannot open file!\n");
                getchar();
                return 1;
        }
        else
        {
                printf("File is now open. Press Enter...\n");
        }
   
    for(i = 0; i < nRow; i++) {
        for(j = 0; j < nCol; j++) {
            fscanf(fpIn, "%d", &data[i][j]);
        }     
    }   
    printf("file has been read in\n");
    printf("the first entry is:\n");
    printf("%d\n", &data[1][0]);
     
    getchar(); 
    fclose(fpIn);               
       
        return 0;       
}

---

File Opening is done before the if else condition in the else part there is only a printf statement

Do you agree it will work

:)

I missed the "return 1" at first, and wrote a post.

Then I edited the post right afterward, when I saw the "return 1".

What I was trying to say is that the else part of the if statement, is completely unnecessary. The marriage of the two posts turned into something rather foobar, surely. :)

Its OK ADAK it happens just take a chill pill :)

If I use:

Code:

---

double data[100][6];

---

And then in the body of the two for loops:

Code:

---

    for(i = 0; i < nRow; i++) {
        for(j = 0; j < nCol; j++) {
            fscanf(fpIn, "%lf", &data[i][j]);
        }     
    }   
    printf("file has been read in\n");
    printf("the first entry is:\n");
    printf("%lf\n", &data[0][0]);

---

All that gets returned is 0.00000. I'm starting to get really fed up with C and this assignment.

Apparently, I can do the same procedure with fgets and sscanf (our notes mention a spotty example of this). fgets pulls in each line essentially, but how would I read that to each row of 'data' using sscanf?

Code:

---

while(fgets(data, LINE_LENGTH, fpIn) != NULL)
{
sscanf(data, ????);
}

---

Why are you trying to print the address of data[0][0]? Why not print the actual value instead?