Question

So i’m writing a statistical calculator program, and the first function I started to write was the mean calculator. My issue is that I’m getting extremely large( and wrong) values for the answers.

Please Enter a number of inputs
 4
Please enter number 1
 1
Please enter number 2
 2
Please enter number 3
 3
Please enter number 4
 4
Statistical Calculator Menu
(1) Mean
(2) Standard Deviation
(3) Range
(4) Restart/Exit
 1
3940705125981218000000000000000000.000000

Here is my source code.

const int MAX_DATA=5;
void menu(float numbers[], int amount);
float mean(float numbers[],int amount);

int main() 
{ 
int i, amount;
float numbers[MAX_DATA];

printf("Please Enter a number of inputs \n");
scanf("%d", &amount);
if (amount>MAX_DATA){
              printf("You entered too many numbers");
             }else{  

for (i=1;i<amount+1;i++){
    printf("Please enter number %d\n", i);
    scanf("%f",&numbers[i]);
    }
      menu(numbers,amount);
}  
    getch();
return 0;
}

void menu(float numbers[],int amount)
{
 int input2;
 printf("Statistical Calculator Menu");
 printf("\n(1) Mean\n(2) Standard Deviation\n(3) Range\n(4) Restart/Exit");
 scanf("%d",&input2);
      if(input2==1){
         mean(numbers,amount);
        }

}

float mean(float numbers[],int amount)
{
 int i;
 float sum;
 float average;
 for (i=0; i<amount;i++){
     sum=sum+numbers[i];
     }
     average=sum/amount;
     printf("%f", average);

  return average;   
}

Can someone point out the mistake, or explain why this isn’t calculating correctly?

Answer 1

You are not initialising sum so it is taking whatever garbage value was last in that place on the stack. Change:

float sum;

To:

float sum = 0;

Another problem you have is:

for(i = 1; i < amount + 1; i++) {
    printf("Please enter number %d\n", i);
    scanf("%f",&numbers[i]);
}

Array indexes start at 0, so this should be:

for(i = 0; i < amount; i++) {
    printf("Please enter number %d\n", i);
    scanf("%f",&numbers[i]);
}