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how to pass array from one function into another: variance to mean

This is a discussion on how to pass array from one function into another: variance to mean within the C Programming forums, part of the General Programming Boards category; function name implies what it does: i.e. finds mean variance etc. I think the mean is ok. The resultant mean ...

  1. #1
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    how to pass array from one function into another: variance to mean

    function name implies what it does: i.e. finds mean variance etc.
    Name:  Untitled.png
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    I think the mean is ok. The resultant mean in the main function is 6.something, ask you can see from the image.

    But the mean is not right in the variance function, as you can see from a test print. What is wrong with the mean there?

    Code:
    #include<stdio.h>
    #include<math.h>
    
    
    double mean(int marks[], int n);
    double variance(int marks[], int n);
    double stdDev(int marks[], int n);
    double mode(int marks[], int n);
    void sort(int marks[], int n);
    
    
    int main(){
        
        int n,i;
        double t1, t2, t3, t4;
        
    
    
    
    
        
    
    
    
    
    
    
        FILE *inFile;
    
    
        inFile=fopen("marks.txt", "r");
        if (inFile==NULL)
        {
            printf("File open error!\n");
            return 0;
        }
        
        n=0;
        int count[10000];
        
        
        
        while((fscanf(inFile, "%d", &count[n]))==1) n++;
        int marks[n];
        for(i=0; i<n; i++) marks[i]=count[i];
    
    
        printf("%d is the number of readings\n", n);
        /*printf("testing marks array %d %d %d %d %d", marks[0], marks[1], marks[2], marks[812], marks[813]);*/
    
    
    
    
        t1=mean(marks, n);
    /*printf("testing marks array %d %d %d %d %d", marks[0], marks[1], marks[2], marks[812], marks[813]);*/
    
    
    
    
        t2=variance(marks, n);
    /*printf("testing marks array %d %d %d %d %d", marks[0], marks[1], marks[2], marks[812], marks[813]);*/
    
    
    
    
        t3=stdDev(marks, n);
    /*printf("testing marks array %d %d %d %d %d", marks[0], marks[1], marks[2], marks[812], marks[813]);*/
    
    
    
    
        t4=mode(marks, n);
    /*printf("testing marks array %d %d %d %d %d", marks[0], marks[1], marks[2], marks[812], marks[813]);*/
    
    
    
    
    
    
        printf("%lf %d %lf %d, mean, variance, stdDev, mode", t1, t2, t3, t4);
        fclose(inFile);
        return 0;
    }
    
    
    
    
    double mean(int marks[], int n){
        int i;
        int sum=0;
        for(i=0; i<n; i++) sum+=marks[i];
        return (1.0*sum/n);
    }
    
    
    double variance(int marks[], int n){
        int i;
        double ave, varsum;
        varsum=0;
        printf("%d %d %d marks test\n", marks[0], marks[1], marks[813]);
        
        ave=mean(marks, n);
        printf("%d ave test\n", ave);
        for (i=0; i<n; i++) varsum+=(marks[i]-ave)*(marks[i]-ave);
        printf("%d varsum, %d variance test \n", varsum, varsum/n);
        return (varsum/n);
    }
    double stdDev(int marks[], int n){
        int i;
        double var;
        var=variance(marks, n);
        return (sqrt(var));
    }
    
    
    double mode(int marks[], int n){
        int i, count=0;
        double mid;
        mid=n/2.0;
        sort(marks, n);
        for(i=0; i<n; i++){
            count=+marks[i];
            if (count==mid) return ((marks[i]+marks[i+1])/2.0); 
            if (count>mid) return(marks[i]);}
            return 0;
    
    
    
    
        } 
    
    
        void sort(int marks[], int n){
            int sorter[n];
            sorter[0]=marks[0];
            int i, temp;
            for(i=1; i<n; i++){
                if (marks[i]>=sorter[i]) sorter[i+1]=marks[i];
                else { 
                    temp=sorter[i];
                    sorter[i]=marks[i];
                    sorter[i+1]=temp;
                }
            }
    
    
                for (i=0; i<n; i++) marks[i]=sorter[i];
                return;}

  2. #2
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    So how many threads do you plan to start for the same problem?

    (Please tell me now so I can ignore them... )

  3. #3
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    it's no longer segmentation error, so i cannot continue with the same thread

  4. #4
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    Quote Originally Posted by nanobot View Post
    it's no longer segmentation error, so i cannot continue with the same thread
    It's the same program....
    Sprouting 324,675,123 threads over it isn't going to make you any friends.

  5. #5
    and the hat of wrongness Salem's Avatar
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    Perhaps you could do
    gcc -Wall prog.c

    and see that all the format flags to your final printf are wrong.
    rags_to_riches likes this.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  6. #6
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    thanks a lot, changed the variable types several times so I messed up . Going to fix mode function now

  7. #7
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    Code:
    void sort(int marks[], int n){        int sorter[n]={0};
            sorter[0]=marks[0];
            int i, temp;
            for(i=1; i<n; i++){
                if (marks[i]>=sorter[i]) sorter[i+1]=marks[i];
                else { 
                    temp=sorter[i];
                    sorter[i]=marks[i];
                    sorter[i+1]=temp;
                }
            }
    
    
                for (i=0; i<n; i++) marks[i]=sorter[i];
                return;}
    After I intialized the sorter array in the function to zero, this error appears: variable sized objects may not be intialized
    excess elements in array intializer
    near intialization for 'sorter'

    this is the correct way to intialize all elements of array to 0, right?

  8. #8
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    No.

    Just do this:
    Code:
    void sort(int marks[], int n)
      {     
            int i, j, temp;
            for(i=0; i<n; i++)
              for (j = i; j< n; j++)
                if (marks[i] < marks[j])
                  {
                    temp=marks[i];
                    marks[i]=marks[j];
                    marks[j]=temp;
                  }
      }
    If you're going to work off a copy of the array...
    sort the copy then copy it back to the original...
    but you can just as easily do it right in the original array.

  9. #9
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    thanks a lot for the tip

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