Storing # from Data File in Arrays?

This is a discussion on Storing # from Data File in Arrays? within the C Programming forums, part of the General Programming Boards category; Hi I was wondering if it was possible to store a data file in an array: The data file (vec_in.dat) ...

  1. #1
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    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]?

  2. #2
    Why bbebfe is not bbebfe? bbebfe's Avatar
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    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, "&#37;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.

  3. #3
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    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?

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    Code:
    printf("%.6f", v[k]);
    And you expect this to print more than one number because why?

  5. #5
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    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 ]

  6. #6
    and the Hat of Guessing tabstop's Avatar
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    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.

  7. #7
    Why bbebfe is not bbebfe? bbebfe's Avatar
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    Ah, you have three problems in your code still.
    1. I have no idea about if there is a convenient way to use array with sscanf, the ugly way here is :
    Code:
    sscanf(text, "&#37;lf %lf %lf %lf %lf", v, v+1, v+2, v+3, v+4);
    Remeber, array is pointer and pointer is array on some occasions. So, you needn't dereference an array identifier when you need a pointer to the array.

    2. array index starts with 0 nor 1. so there are problems within you loop structure.
    Code:
            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;
            }
    3. the third is what tabstop said, you need adding a loop structure to print all elements of an array.
    Code:
    		printf("\nOriginal Vector = [");
    		for (k = 0; k < 5; k++) {
    			printf("%.6f ", v[k]);
    		}
    		printf(" ]\n");
    		printf("\nNormalized Vector = [");
    		for (k = 0; k < 5; k++) {
    			printf("%.6f ", vec[k]);
    		}
    		printf(" ]\n");
    below is the code I have modified, it generates the output what you want.
    Code:
    #include <stdio.h>
    #include <math.h>
    #include <stdlib.h>
    int main(){
        int k;
        char text[81];
        double v[5], vec[5];
        double norm, mid;
        FILE *Inf_1, *Outf_1;
    
    	mid = 0;
    	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 %lf %lf %lf %lf", v, v+1, v+2, v+3, v+4);
            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 = [");
    		for (k = 0; k < 5; k++) {
    			printf("%.6f ", v[k]);
    		}
    		printf(" ]\n");
    		printf("\nNormalized Vector = [");
    		for (k = 0; k < 5; k++) {
    			printf("%.6f ", vec[k]);
    		}
    		printf(" ]\n");
    	    
    		fprintf(Outf_1,"\nOriginal Vector = [");
    		for (k = 0; k < 5; k++) {
    			fprintf(Outf_1,"%.6f", v[k]);
    		}
    		fprintf(Outf_1," ]\n");
    
    		fprintf(Outf_1,"\nNormalized Vector = [");
    		for (k = 0; k < 5; k++) {
    			fprintf(Outf_1,"%.6f", vec[k]);
    		}
    		fprintf(Outf_1,"\n");
    
        
        fclose(Inf_1);
        fclose(Outf_1);
    	system("pause");
        exit(0);
    }
    Last edited by bbebfe; 11-13-2008 at 08:10 PM.

  8. #8
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    Problem solved! I defined the variables in the "ugly way" at first but I tried to find a more elegant solution. I tried putting sscanf in the k loop but I didn't know how to stop it from scanning the same number over and over. I guess I have to settle. Thanks!
    Last edited by dakarn; 11-13-2008 at 08:18 PM.

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