Thread: can someone help me with this?

Originally Posted by burninfrost296

...
the two sections are different
one has printf("%9.3f", a[row]+col);
and the other has printf("%9.3f", a[row][col]);
i need both

AEach green section has both, given that the second green section is identical to the last six lines of the first green section. The first prints the a matrix that you want. The red section prints your b as you read it in. The third green section prints another row of a, if there was one, which there isn't, so it does weird things. You do not want to try to print a's after you read and print the b's, so simply remove the extraneous green section.

oh
haha
i get it now
thanks, but when i compile it, it still prints 4 rows and 7 columns instead of 7 rows and 7 columns
do you know why it does that?

<< Yes >>

Seriously, post your most recent version of the program, and I'll take a look and see what's up, OK?

ok
thanks

#include <stdio.h>
int main(void)
{
FILE *infile;
int row, col, rows, cols;
double **a, *b, *c, sum=0.0;
/* Define infile */
infile = fopen("matrix5.dat", "r");
if(infile==NULL)
{
printf("matrix5.dat does not exist.\n");
exit(100);
}
/* read rows and cols */
fscanf(infile, "%d %d", &rows, &cols);
printf("\nrows = %2d cols = %2d\n", row, cols);
/* Allocate memory to **a */
a=(double **)calloc((size_t)rows, sizeof(double *));
/* Allocate memory for a[row], row=0, 1, ..., rows-1 */
for(row = 0; row<rows; row++)
{
a[row] = (double *)calloc((size_t)cols, sizeof(double));
if(a[row] == NULL)
{
printf("\n**calloc failed in allocating memory for a[%d]
\n", row);
exit(101);
}
}
/* Allocate memory for b[rows] and c[rows] */
b = (double *)calloc((size_t)rows, sizeof(double));
c = (double *)calloc((size_t)rows, sizeof(double));
if(b==NULL || c==NULL)
{
printf("** calloc failed in allocating memory for b[] or c[]\n")
;
exit(102);
}
/* read all rows and save the values in a[][] */
printf("\na[][]:\n");
for(row=0; row<rows; row++)
{
printf("[%d]", row);
for(col=0; col<cols; col++)
fscanf(infile, "%lf", a[row]+col);
for(col=0; col<cols; col++)
printf("%9.3f", a[row][col]);
printf("\n");
}
/* read b[] from the last line */
printf("\nb[]");
for(row=0; row<rows; row++)
fscanf(infile, "%lf", b+row);
for(row=0; row<rows; row++)
printf("%9.3f", b[row]);
printf("\n");
/* print a[][] */
/* print b[] */
/* compute c[] = a[][] * b[] */
for(row=0; row<rows; row++)
{
for(col=0, sum=0.0; col<cols; col++)
sum = sum + (a[row][col] *b[col]);
c[row]=sum;
}
printf("\n");
/* print c[] */
printf("c[]");
for(row=0; row<rows; row++)
printf("%9.3f", c[row]);
printf("\n");
/* return memory */
free(b);
free(c);
for(col = 0; col<cols; col++)
free(a[col]);
free(a);
/* close infile */
fclose(infile);
exit(0);
}

Because you read the number of rows into the variable called "rows" and then print the variable called "row".