Use arrays to talley ratings and give average

**new2cstudent** · 09-26-2010

I am working on a program that should tally the ratings of a product. There are 5 rating levels from 1 to 5 and 40 different ratings. The program should print out the ratting tallies for each of the 5 rating levels and rpint the average rating for the product. Here is what I have so far. I have commented out some of the parts I havnt totally figured out yet.

Code:

#include <stdio.h>

#define MAX_RATERS 40

#define NUM_RATING_LEVELS 6

int main ()

{
        int i, j;
        int avg;
        int ratings[MAX_RATERS] = {1, 2, 1, 4, 3, 5, 4, 2, 3, 5, 4, 1, 3, 3, 1, 5, 3, 3, 2, 2, 4, 5, 2, 1, 3, 4, 2, 5, 1, 4, 5, 1, 2, 5, 1, 4, 3, 1, 3, 5};
        int stars[NUM_RATING_LEVELS];
        float sum = 0;

        //stars[ratings[i]] = stars[ratings[i]] + 1;

	for (i = 0; i < MAX_RATERS; i++)
        {   stars[ratings[i]] = stars[ratings[i]] + 1;
		
                
          // for (j = 0; j <= stars[i]; j++)  
          //    printf("%d, %d", i, ratings[i]);
        }

	
	     /* for (i = 0; i < 40; i++); //this calculates the average of all the ratings
                sum += ratings[i];
                avg = sum/40;

         printf("the average rating for the product is %d\n", avg);*/

return 0;
}

**kmdv** · 09-26-2010

What's the question?

**new2cstudent** · 09-26-2010

I would like to count out the and tally the ratings. A total of all the ones, twos, threes, fours and fives and then average them all. Something like this...

stars[1] = 5
stars[2] = 5
stars[3] = 10
stars[4] = 10
stars[5] = 10
The average rating is: 3.38

So I cant figure out how to get the ratings sumed and then in nice columns

**kmdv** · 09-26-2010

I still can't see the question

You should post a sample program (without the comments) that is supposed to work.

**new2cstudent** · 09-26-2010

How about something simple first. Why wont this work? I want to know the sum of this array. So I put the Ratings[] in for it to Sum. I get this huge negative number. I know that there are 40 ratings so it fits in my array, but still gives me a negative.

Code:

#include <stdio.h>

#define MAX_RATERS 40

#define NUM_RATING_LEVELS 6

int main ()

{
        int i, j;
        int avg;
        int ratings[MAX_RATERS] = {1, 2, 1, 4, 3, 5, 4, 2, 3, 5, 4, 1, 3, 3, 1, 5, 3, 3, 2, 2, 4, 5, 2, 1, 3, 4, 2, 5, 1, 4, 5, 1, 2, 5, 1, 4, 3, 1, 3, 5};
        //int stars[NUM_RATING_LEVELS];
        int sum = 0;

        

	
	      for (i = 0; i < MAX_RATERS; i++); 
                sum = sum + ratings[i];
                avg = sum/40;

         printf("the sum rating for the product is %d\n", sum);

return 0;
}

**rags_to_riches** · 09-26-2010

Code:

for (i = 0; i < MAX_RATERS; i++);

That semi-colon at the end is the problem. It makes the loop do nothing.

**Jamdog** · 09-26-2010

Remove the semi-colon from the for loop (shown in red below). It's preventing the 2nd line below from being looped.

Code:

for (i = 0; i < MAX_RATERS; i++); 
                sum = sum + ratings[i];

EDIT: lol - beaten to it...

**Char*Pntr** · 09-26-2010

Originally Posted by new2cstudent

How about something simple first. Why wont this work? I want to know the sum of this array. So I put the Ratings[] in for it to Sum. I get this huge negative number. I know that there are 40 ratings so it fits in my array, but still gives me a negative.

Code:

#include <stdio.h>

#define MAX_RATERS 40

#define NUM_RATING_LEVELS 6

int main ()

{
        int i, j;
        int avg;
        int ratings[MAX_RATERS] = {1, 2, 1, 4, 3, 5, 4, 2, 3, 5, 4, 1, 3, 3, 1, 5, 3, 3, 2, 2, 4, 5, 2, 1, 3, 4, 2, 5, 1, 4, 5, 1, 2, 5, 1, 4, 3, 1, 3, 5};
        //int stars[NUM_RATING_LEVELS];
        int sum = 0;

        

	
	      for (i = 0; i < MAX_RATERS; i++); 
                sum = sum + ratings[i];
                avg = sum/40;

         printf("the sum rating for the product is %d\n", sum);

return 0;
}

First I see a semicolon next to your FOR loop! get rid of that.

Edit: since your for loop only has one statement, it won't need curly braces
as I originally suggested. However, the curly braces would make things more clear.

Would it be too rash if I suggested making "avg" a float?

**new2cstudent** · 09-26-2010

Right, thanks, I should have seen that. So now I got an average of 2, but the real average is 2.95. So I changed my float to a double and changed the &d to a %6.2lf. I want to get the 2 decimal places. But all that prints is -0.00 any ideas?

Code:

#include <stdio.h>

#define MAX_RATERS 40

#define NUM_RATING_LEVELS 6

int main ()

{
        int i, j;
        int avg;
        int ratings[MAX_RATERS] = {1, 2, 1, 4, 3, 5, 4, 2, 3, 5, 4, 1, 3, 3, 1, 5, 3, 3, 2, 2, 4, 5, 2, 1, 3, 4, 2, 5, 1, 4, 5, 1, 2, 5, 1, 4, 3, 1, 3, 5};
        //int stars[NUM_RATING_LEVELS];
        double sum = 0;

        
	      for (i = 0; i < 40; i++) //this calculates the average of all the ratings
                sum += ratings[i];
                avg = sum/40;

         printf("the avg rating for the product is %6.2lf\n", avg);

return 0;
}

**Adak** · 09-26-2010

You need to change your array, imo.

Ratings are made FOR a <product, students, etc.> given SCORES, in a one to many, relationship (usually).

Think of STUDENTS with test SCORES:

Code:

Name    Scores
======================
Abby  20  22  18  90          (row 0)  Average Abby score, here
Bob   15  20  17  77          (row 1)   Average Bob score, here
Chris 21  20  19  91          (row 2)   Average Chris score, here
======================
Average test score here
      18  21  18  86         (just guesses on numbers)

So we can get 1) Each students average score or 2) the average score of all the students, for each quiz and test.

In the first instance, we sum up the scores along the row, and in the second instance we sum up the scores along the columns.

imo, you need to add a second array to your program, and keep this relationship: the names of the product in a row index[row][col] correspond to the products data [row][col]

Like in the above, Abby's scores are on score[0][N], and her name is in students[0][N]

Your code (first post) has this:

Code:

	      for (i = 0; i < MAX_RATERS; i++); 
                sum = sum + ratings[i];
                avg = sum/40;

         printf("the sum rating for the product is %d\n", sum);


and needs this:

	      for (i = 0; i < MAX_RATERS; i++) 
                sum += ratings[i];
              avg = sum/40;

         printf("the sum rating for the product is %d\n", sum);

And integer division will cut off (truncate as they call it), any remainder. To keep it, use double or float data types.

**Char*Pntr** · 09-26-2010

Originally Posted by new2cstudent

Right, thanks, I should have seen that. So now I got an average of 2, but the real average is 2.95. So I changed my float to a double and changed the &d to a %6.2lf. I want to get the 2 decimal places. But all that prints is -0.00 any ideas?

Code:

#include <stdio.h>

#define MAX_RATERS 40

#define NUM_RATING_LEVELS 6

int main ()

{
        int i, j;
        int avg;
        int ratings[MAX_RATERS] = {1, 2, 1, 4, 3, 5, 4, 2, 3, 5, 4, 1, 3, 3, 1, 5, 3, 3, 2, 2, 4, 5, 2, 1, 3, 4, 2, 5, 1, 4, 5, 1, 2, 5, 1, 4, 3, 1, 3, 5};
        //int stars[NUM_RATING_LEVELS];
        double sum = 0;

        
	      for (i = 0; i < 40; i++) //this calculates the average of all the ratings
                sum += ratings[i];
                avg = sum/40;

         printf("the avg rating for the product is %6.2lf\n", avg);

return 0;
}

You probably forgot to change your format specifier in the printf() to %f.

Also you'll need to change int 40 to type float as well in your calculation,

Edit:
ADAK already pointed out using int in division. Sorry about that!

But that will fix your result. :-)

**new2cstudent** · 09-26-2010

I still cant figure this part out.

I had this...

Code:

for (i = 0; i < MAX_RATERS; i++) 
                sum += ratings[i];
                avg = sum/40;
        
        printf("the avg rating for the product is %d\n", avg);

and I got and avg of 2

and changed to this...

Code:

        int i, j;
        int avg;
        int ratings[MAX_RATERS] = {1, 2, 1, 4, 3, 5, 4, 2, 3, 5, 4, 1, 3, 3, 1, 5, 3, 3, 2, 2, 4, 5, 2, 1, 3, 4, 2, 5, 1, 4, 5, 1, 2, 5, 1, 4, 3, 1, 3, 5};
        //int stars[NUM_RATING_LEVELS];
        float sum = 0;

        for (i = 0; i < MAX_RATERS; i++) 
                sum += ratings[i];
                avg = sum/40.0;

         printf("the avg rating for the product is %6.2f\n", avg);
[

and I get -24659887545etc

what happened?

**new2cstudent** · 09-26-2010

Figured it out, I needed to change my average to a float as well.

**Char*Pntr** · 09-26-2010

Originally Posted by new2cstudent

Figured it out, I needed to change my average to a float as well.

That was one of my first "rash" suggestion! I suggest you slowly re-read all
of the responses on this thread.

**new2cstudent** · 09-26-2010

Now I am trying to figure out how to sort or count the ratings. Tally up the 1s 2s etc. I have put a loop in another loop. Here it is...

Code:

#include <stdio.h>

#define MAX_RATERS 40

#define NUM_RATING_LEVELS 6

int main ()

{
        int i, j;
        float avg;
        int ratings[MAX_RATERS] = {1, 2, 1, 4, 3, 5, 4, 2, 3, 5, 4, 1, 3, 3, 1, 5, 3, 3, 2, 2, 4, 5, 2, 1, 3, 4, 2, 5, 1, 4, 5, 1, 2, 5, 1, 4, 3, 1, 3, 5};
        int stars[NUM_RATING_LEVELS];
        float sum = 0;

        //stars[ratings[i]] = stars[ratings[i]] + 1;

	for (i = 0; i < NUM_RATING_LEVELS; i++)
        {  	printf("%dstars:, %d\n", i, stars[i]);
			for (j = 0; stars[ratings[i]] = stars[ratings[i]] + 1; j++)
			{	printf("%d\n", ratings[j]);
			}
}
	      for (i = 0; i < MAX_RATERS; i++) 
                sum += ratings[i];
                avg = sum/40.00;

         printf("the avg rating for the product is %6.2f\n", avg);

return 0;
}

im still not seeing how to get the tally of each rating. If I use a IF statement saying if rating[] =<5 print sum?

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Use arrays to talley ratings and give average