Thread: Storing # from Data File in Arrays?

Hi I was wondering if it was possible to store a data file in an array:

The data file (vec_in.dat) would look like this :

Code:

1.2 -2.3 0.53 2.01 -1.5

I'm trying to store these 5 numbers in an array called v[5]. I want to manipulate the data in v[5] and spit out a product stored in vec[5]. Then I want to print the output onto a screen and a data file.

This is my code so far:

Code:

#include <stdio.h>
#include <math.h>
int main(){
int k;
double text[81], v[5], vec[5];
double norm, mid;
FILE *Inf_1, *Outf_1;
Inf_1 = fopen("vec_in.dat", "r");
Outf_1 = fopen("vec_out.dat", "w");
if ((Inf_1 == NULL) || (Outf_1 == NULL))
{
printf("Error oepning the file\n");
exit(1);
}
while(fgets(text,81,Inf_1)!=NULL)
  {  
sscanf(text, "%lf", &v);
for (k=0; k<=5; k++) {
mid += pow(v[k],2);
}
norm = sqrt(mid);
for (k=0; k<=5;k++) {
vec[k] = v[k]/norm;
}
}
printf("\nOriginal Vector = [");
printf("%.6f", v[k]);
printf(" ]\n");
printf("\nNormalized Vector = [");
printf("%.6f", vec[k]);
printf(" ]\n");

fprintf(Outf_1,"\nOriginal Vector = [");
fprintf(Outf_1,"%.6f", v[k]);
fprintf(Outf_1," ]\n");
fprintf(Outf_1,"\nNormalized Vector = [");
fprintf(Outf_1,"%.6f", vec[k]);
fprintf(Outf_1,"\n");

fclose(Inf_1);
fclose(Outf_1);
exit(0);
}

Currently, I'm getting these errors:
15 q3.c
warning: passing arg 1 of `fgets' from incompatible pointer type
17 q3.c
warning: passing arg 1 of `sscanf' from incompatible pointer type

Am I using the fgets correctly? Is v[k] being properly converted to vec[k]?

You have at least 4 problems in your code.
1. Never use literal value as the size of array, using sizeof instead.

Code:

while(fgets(text, sizeof(text), Inf_1)!=NULL)

2. text is an array of double, but fgets and sscanf need a pointer to char.

Code:

while(fgets(text,81,Inf_1)!=NULL) {
...
sscanf(text, "%lf", &v);

You should change the definition of array text from double to char.

Code:

char text[81];

3. You are using += operator, but variable mid has never initialized, as of it's a local variable, its initialized value isn't 0.

Code:

mid = 0;
...
mid += pow(v[k],2);

4. function exit is defined in stdlib.h, you should add it in your program.

Those tips are great. Thank you very much.

My code is compiling but my vectors aren't being stored correctly. This is my output:

iacs5.ucsd.edu% a.out

Original Vector = [2.000000 ]

Normalized Vector = [0.000000 ]

I want my output to look like this:

Original Vector = [ 1.200000 -2.300000 0.530000 2.010000 -1.500000 ]

Normalized Vector = [ 0.329033 ............................. -0.411291 ]

This is my edited code (able to compile):

Code:

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

int main(){
int k;
double v[5], vec[5];
char text[81];
double norm, mid = 0;
FILE *Inf_1, *Outf_1;
Inf_1 = fopen("vec_in.dat", "r");
Outf_1 = fopen("vec_out.dat", "w");
if ((Inf_1 == NULL) || (Outf_1 == NULL))
{
printf("Error oepning the file\n");
exit(1);
}
while(fgets(text,sizeof(text),Inf_1)!=NULL)
  {  
sscanf(text, "%lf", &v);
for (k=0; k<=5; k++) {
mid += pow(v[k],2);
}
norm = sqrt(mid);
for (k=0; k<=5;k++) {
vec[k] = v[k]/norm;
}
}
printf("\nOriginal Vector = [");
printf("%.6f", v[k]);
printf(" ]\n");
printf("\nNormalized Vector = [");
printf("%.6f", vec[k]);
printf(" ]\n");

fprintf(Outf_1,"\nOriginal Vector = [");
fprintf(Outf_1,"%.6f", v[k]);
fprintf(Outf_1," ]\n");
fprintf(Outf_1,"\nNormalized Vector = [");
fprintf(Outf_1,"%.6f", vec[k]);
fprintf(Outf_1,"\n");

fclose(Inf_1);
fclose(Outf_1);
exit(0);
}

... and this is the input file I want it to read (vec_in.dat):

Code:

1.2 -2.3 0.53 2.01 -1.5

Why is the array only returning one value?

Code:

printf("%.6f", v[k]);

And you expect this to print more than one number because why?

It seems the print only v[0] if I explicitly tell it to print v[0], v[1], v[2] etc

Code:

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

int main(){
int k;
double v[6], vec[6];
char text[81];
double norm, mid = 0;
FILE *Inf_1, *Outf_1;
Inf_1 = fopen("vec_in.dat", "r");
Outf_1 = fopen("vec_out.dat", "w");
if ((Inf_1 == NULL) || (Outf_1 == NULL))
{
printf("Error oepning the file\n");
exit(1);
}
printf("\nOriginal Vector = [");
while(fgets(text,sizeof(text),Inf_1)!=NULL)
  {
sscanf(text, "&#37;lf", &v);
for (k=0; k<=5; k++) {
printf("%.6f ", v[k]);
mid += pow(v[k],2);
}
norm = sqrt(mid);
for (k=0; k<=5;k++) {
vec[k] = v[k]/norm;
}
}
printf(" ]\n");
printf("\nNormalized Vector = [");
printf("%.6f", vec[k]);
printf(" ]\n");

fprintf(Outf_1,"\nOriginal Vector = [");
fprintf(Outf_1,"%.6f", v[k]);
fprintf(Outf_1," ]\n");
fprintf(Outf_1,"\nNormalized Vector = [");
fprintf(Outf_1,"%.6f", vec[k]);
fprintf(Outf_1,"\n");

fclose(Inf_1);
fclose(Outf_1);
exit(0);
}

Output:
iacs5.ucsd.edu% gcc q3.c -lm
iacs5.ucsd.edu% a.out

Original Vector = [1.200000 0.000000 0.000000 0.000000 0.000000 0.000000 ]

Normalized Vector = [1.200000 ]

If you want a statement to be repeated more than once, you must use a looping construct of some kind. Since you aren't, it won't be.