CODEWITHSUNDEEP
cmatrixinput
Gerard22
Gerard22

Reputation: 363

Reading a matrix of numbers from a txt file

So, I created a matrix on a text file, which looks like this:

1.0#2.2#3.4
3.4#5.5#1.0
6.6#5.5#1.0

I need my script to read each number on the line, add them and then create a new matrix with the result of dividing each number for the sum of the whole line. Example:

1.0+2.2+3.4 = 6.6

The first line of the second matrix that I will create will be: 

0.15#0.33#0.51 (because 1.0/6.6 is 0.15 etc.)

Now I can print the whole matrix but I can't get my head on how to save each number of the line as a variable and add it to the next numbers, any suggestion on this?

This is my current work:

#include <stdio.h>
#include <stdlib.h> 

int main() {
    FILE *fptr;
    double c;

    // Open file
    fptr = fopen("mat.txt", "r");
    if (fptr == NULL) {
        printf("Cannot open file \n");
        exit(0);
    }

    // Read contents from file
    c = fgetc(fptr);
    while (c != EOF) {
        printf ("%c", c);
        c = fgetc(fptr);
    }

    fclose(fptr);
    return 0;
}

Upvotes: 1

Views: 307

Answers (2)

satyaGolladi
satyaGolladi

Reputation: 192

Below method uses dynamic memory allocation

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

int main()
{
    size_t x = 3, y = 3;
    int ret, i, j;
    FILE *fptr_in , *fptr_out;
    double (*d)[y], sum = 0;
    d = malloc( sizeof(double) * x * y );
    assert(d != NULL);
    // Open file
    fptr_in = fopen("mat.txt", "r");
    assert(fptr_in != NULL);

    /*file to write output*/
    fptr_out = fopen("mat_out.txt", "w");
    assert(fptr_out != NULL);

    for(i = 0; i < x; i++){
        sum = 0;
        for(j = 0; j < y; j++){
            ret = fscanf(fptr_in, "%lf", &d[i][j]);
            assert(ret > 0);
            sum += d[i][j];
        }
        for(j = 0; j < x; j++){
            ret = fprintf(fptr_out, "%lf ", d[i][j]/sum);
        }
        fprintf(fptr_out, "\n");
    }
    free(d);
    fclose(fptr_in);
    fclose(fptr_out);
    return 0;
}

Upvotes: 0

kiran Biradar
kiran Biradar

Reputation: 12732

Assuming your matrix will be of size 3*3 always and # is the deliminator, in that case you can use fscanf to read 3 values in while loop like below.

#include <stdio.h>
#include <stdlib.h>

int main()
{
    FILE *fptr;
    double a=0,b=0,c=0;
    double matrix[3][3];

    // Open file
    fptr = fopen("mat.txt", "r");
    if (fptr == NULL)
    {
        printf("Cannot open file \n");
        exit(0);
    }

    int i =0;
   /*fscanf reads the 3 values each time into a,b and c*/
    while (fscanf(fptr,"%lf#%lf#%lf", &a,&b,&c) == 3)
    {
        double sum = a+b+c;
        matrix[i][0] = a/sum;
        matrix[i][1] = b/sum;
        matrix[i][2] = c/sum;
        i++;
    }

    for (i=0;i<3;i++)
     printf ("%lf %lf %lf\n", matrix[i][0],matrix[i][1],matrix[i][2]);

    fclose(fptr);
    return 0;
}

Upvotes: 2

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