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?
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]);
}
Apart from what Mike said,
for (i=1;i<amount+1;i++)
{
printf("Please enter number %d\n", i);
scanf("%f",&numbers[i]);
}
float mean(float numbers[],int amount)
{
// ..
for (i=0; i<amount;i++){
sum=sum+numbers[i];
}
....
From this, you are not filling numbers[0]. But in the mean calculation, using the value at 0 index.
float sum;
float average;
for (i=0; i<amount;i++){
sum=sum+numbers[i];
}
sum is not initialized in your program.
Related
In my C Program, I want to get the average of the sum of numbers being entered until the program stops. What should I add to check the average? Thank you!
#include <stdio.h>
int main (void)
{
int x;
int sum = 0;
int average;
int testEOF;
//Statements
printf("Enter your numbers: <EOF> to stop.\n");
do
{
testEOF = scanf("%d", &x);
if (testEOF !=EOF)
sum +=x;
} while (testEOF !=EOF);
printf ("\nTotal: %d\n", sum);
printf ("\nAverage: %d\n", average);
return 0;
//main
}
As other people explained, you have to initialize sum and count, they are never given their initial values. No need to initialize average and x because you assign sum/count to average and users will assign any value to x.
You have to put everything you want your if statement to do in {...}. But you didn't. Your if statement only does sum +=x and does not work for count++ and average = sum / count. So your program increases the value of count even after EOF. So you found 14/6 rather than 14/5.
You checked testEOF != EOF twice. One is in the if statement, other is in do-while.
I put the code below:
#include <stdio.h>
int main (void){
float x;
float sum = 0;
float count = 0;
float average;
float testEOF;
printf("Enter your numbers: <EOF> to stop.\n");
while(1){
testEOF = scanf("%f", &x);
if (testEOF ==EOF){
break;
}
sum +=x;
count++;
average = sum / count;
}
printf ("\nTotal: %f\n", sum);
printf ("\nAverage: %.2f\n", average);
return 0;
}
#include <stdio.h>
int main (void)
{
float x;
float sum;
float count;
float average;
float testEOF;
//Statements
printf("Enter your numbers: <EOF> to stop.\n");
do
{
testEOF = scanf("%f", &x);
if (testEOF !=EOF)
sum +=x;
count++;
average = sum / count;
} while (testEOF !=EOF);
printf ("\nTotal: %f\n", sum);
printf ("\nAverage: %.2f\n", average);
return 0;
}
This is now almost correct. The only thing is that the number is not getting divided by the number of values entered.
Example:
2
3
3
3
3
Sum is 14
Average: 2.3 (should be 2.8)
This seems that count is being added by 1 every time I get the average.
Well if you want your output to be printed with decimal point you can do the following , in that case
for inputs like 0, 1, 1 the out would be 0.666667 otherwise it will be simply 0 ignoring the decimal part.
the while part can be optimized as suggested by #David C. Rankin
double sum = 0;
double average = 0;
unsigned int count = 0;
//Statements
printf("Enter your numbers: <EOF> to stop.\n");
do
{
testEOF = scanf("%d", &x);
if (testEOF != EOF)
{
sum += x;
count++;
}
} while (testEOF != EOF);
printf ("\nTotal: %f\n", sum);
average = sum / count;
printf ("\nAverage: %f\n", average);
I'm new to C. I've been tasked to run a program that calculates the percentage of students that passed an exam,based on N grade inputs.I don't really understand how functions work in though.This is what I came up with
#include <stdio.h>
#define MAX_N 300
main()
{
int N,grade,i;
float success(N)
{
float sum=0.0;
for (i=0;i<N;i++) {
if (grade>=5) {
sum+=1;
}
float success=sum/N;
return(success);
}
}
printf("How many students? ");
scanf("%d",&N);
printf("Enter grades(0-10) of %d students ",N);
for (i=0;i<N;i++){
scanf("%d",&grade);
}
printf("%f percent of students have passed the exam ",success(N);
return(0);
}
It looks like it should work, however I always get the wrong result.It is stuck on displaying 0.2 or 0.25 for any input I give.Can somebody help?
The problem is that in grade only the last entered data is being stored. Make grade as an array so that all data can be stored.
I guess you are taking multiple value for grade and not taking array for it.
grade should be an array and in loop scanf("%d",&grade[i]); should be implement.
grade should be an array of N integers so that each and every value is stored. You also forgot to multiply success by 100 to get the percentage.
I think I fixed the code:
#include <stdio.h>
#define MAX_N 300
float success(int grade[],int N)
{int i;
float sum=0.0;
for (i=0;i<N;i++) {
if (grade[i]>=5) {
sum+=1;
}
}
float success=sum/N;
return(success*100);
}
int main(){
int N, i;
printf("How many students? ");
scanf("%d",&N);
int grade[N];
printf("Enter grades(0-10) of %d students ",N);
for(i=0;i<N;i++){
scanf("%d", &grade[i]);
}
printf("%f percent of students have passed the exam ", success(grade, N));
return(0);
}
I think you should examine the code I wrote. A little bad code. But it can help.
#include <stdio.h>
int students_success(int *);
int main() {
int n;
printf("How many students?\n");
scanf("%d", &n);
printf("Enter grades(0-10) of %d students\n", n);
int grade;
int pass_std = 0;
for(int i = 0; i < n; ++i) {
scanf("%d", &grade);
pass_std = students_success(&grade);
}
printf("%.2f percent of students have passed exam.\n", (double)pass_std / n);
}
int students_success(int *grade) {
static int pass_std = 0;
if(4 < *grade) {
++pass_std;
}
return pass_std;
}
I've made this program below to calculate the average mark of a student.
Everything works well until I use -1, it is supposed to stop the program as is display the average of all students that have been entered, say Goodbye! and then terminate.
I think my calculations might be wrong though because it is printing the wrong result for the average marks of the students.
Thanks in Advance.
#include <stdio.h>
int main(void)
{
float final_mark(int a_mark1, int a_mark2, int lab_mark, int quiz_mark, int exam_mark);
int i, a_mark1, a_mark2, lab_mark, quiz_mark, exam_mark;
float average_mark = 0.0;
do
{
for (i = 0; i < 2; i++)
{
printf("Enter assignment 1 mark (-1 to quit): ");
scanf("%d", &a_mark1);
if(a_mark1 == -1)
{
average_mark += final_mark(a_mark1, a_mark2, lab_mark, quiz_mark, exam_mark);
if ((average_mark > 1 ) && (average_mark < 100 ))
{
printf("The average student mark is %.2f%% \n", average_mark);
}
printf("Goodbye! \n");
return 0;
}
printf("Enter assignment 2 mark: ");
scanf("%d", &a_mark2);
printf("Enter laboratory mark: ");
scanf("%d", &lab_mark);
printf("Enter quiz mark: ");
scanf("%d", &quiz_mark);
printf("Enter exam mark: ");
scanf("%d", &exam_mark);
printf("Student %d final mark: %.2f \n", i + 1, final_mark(a_mark1, a_mark2, lab_mark, quiz_mark, exam_mark));
}
}
while(a_mark1 != -1);
return 0;
}
float final_mark(int a_mark1, int a_mark2, int lab_mark, int quiz_mark, int exam_mark)
{
float final_mark = a_mark1 * 0.1 + a_mark2 * 0.15 + lab_mark * 0.15 + quiz_mark * 0.1 + exam_mark * 0.5;
return final_mark;
}
I think you need to rethink your logic a little bit. Why not use a while loop to control the flow. Then you can bail out of the program immediately if user inputs -1 right away. You should use an array to store the averages for each student, then you can loop through and find the class average as well.
-Your float final_mark function seems a little sketchy without any parenthesis.
-You should put your function prototype outside of main as well. See below changes.
#include <stdio.h>
#define MAX_STUDENTS 10 //define what the max number of students is
float final_mark(int mark1, int mark2, int lab, int quiz, int exam);
int main()
{
int i = 0, mark1 = 0, mark2 = 0,
lab = 0, quiz = 0, exam = 0;
int num_students;
float students_avg[MAX_STUDENTS] = {0}; //array to hold averages for students
float average = 0;
while (i < MAX_STUDENTS) {
printf("Enter assignment 1 mark (enter -1 to quit):\n");
scanf("%d", &mark1);
if (mark1 == -1)
break; //no more students, break out of while loop
printf("Enter assignment 2 mark: ");
scanf("%d", &mark2);
printf("Enter laboratory mark: ");
scanf("%d", &lab);
printf("Enter quiz mark: ");
scanf("%d", &quiz);
printf("Enter exam mark: ");
scanf("%d", &exam);
average = final_mark(mark1, mark2, lab, quiz, exam);
students_avg[i] = average; //add this average to array
printf("Student # %d average was %.2f\n", i, students_avg[i]);//debug info
i++;
}
num_students = i; //how many students grades did we read?
average = 0; //reset to 0 so we can use below
for (i = 0; i < num_students; i++)
average += students_avg[i];
if (num_students > 0)
printf("Class average is %.2f\n", average/num_students);
else
printf("Goodbye!\n");
return 0;
}
float final_mark(int mark1, int mark2, int lab, int quiz, int exam)
{
//we can just return the calculation
return ((mark1 * 0.1) + (mark2 * 0.15) + (lab * 0.15) + (quiz * 0.1) + (exam * 0.5));
}
Just erase two lines above printf("GOODBYE! \n"); you will get what you want.
maybe you have to initialized mark s variables to 0. and a_mark1 to 0 too if the user enter -1
disclaimer: I'm new to programming
I'm working on this problem
so far ive written this which takes user inputs and calculates an average based on them
#include <stdio.h>
int main()
{
int n, i;
float num[100], sum = 0.0, average;
for(i = 0; i < n; ++i)
{
printf("%d. Enter number: ", i+1);
scanf("%f", &num[i]);
sum += num[i];
}
average = sum / n;
printf("Average = %.2f", average);
return 0;
}
I'd like the user to enter -1 to indicate that they are done entering data; I can't figure out how to do that. so if possible can someone explain or give me an idea as to how to do it
Thank you!
#include <stdio.h>
int main()
{
int i = 0;
float num[100], sum = 0.0, average;
float x = 0.0;
while(1) {
printf("%d. Enter number: ", i+1);
scanf("%f", &x);
if(x == -1)
break;
num[i] = x;
sum += num[i];
i++;
}
average = sum / i;
printf("\n Average = %.2f", average);
return 0;
}
There is no need for the array num[] if you don't want the data to be used later.
Hope this will help.!!
You just need the average. No need to store all the entered numbers for that.
You just need the number inputs before the -1 stored in a variable, say count which is incremented upon each iteration of the loop and a variable like sum to hold the sum of all numbers entered so far.
In your program, you have not initialised n before using it. n has only garbage whose value in indeterminate.
You don't even need the average variable for that. You can just print out sum/count while printing the average.
Do
int count=0;
float num, sum = 0;
while(scanf("%f", &num)==1 && num!=-1)
{
count++;
sum += num;
}
to stop reading at -1.
There is no need to declare an array to store entered numbers. All you need is to check whether next entered number is equal to -1 and if not then to add it to the sum.
Pay attention to that according to the assignment the user has to enter integer numbers. The average can be calculated as an integer number or as a float number.
The program can look the following way
#include <stdio.h>
int main( void )
{
unsigned int n = 0;
unsigned long long int sum = 0;
printf("Enter a sequence of positive numbers (-1 - exit): ");
for (unsigned int num; scanf("%u", &num) == 1 && num != -1; )
{
++n;
sum += num;
}
if (n)
{
printf("\nAverage = %llu\n", sum / n);
}
else
{
puts("You did not eneter a number. Try next time.");
}
return 0;
}
The program output might look like
Enter a sequence of positive numbers (-1 - exit): 1 2 3 4 5 6 7 8 9 10 -1
Average = 5
If you need to calculate the average as a float number then just declare the variable sum as having the type double and use the corresponding format specifier in the printf statement to output the average.
I'm writing a statistical calculator, with 3 different calculation options. The problem is whenever I choose the 2nd option, it wants to print both the answer from the 1st option and the 2nd option. When I choose the 3 option, it just prints the answer the the 3rd option(the wrong answer, but thats probably a mishap in the formula). Here is the results:
Please Enter a number of inputs
3
Please enter number 1
1
Please enter number 2
2
Please enter number 3
3
Statistical Calculator Menu
(1) Mean
(2) Standard Deviation
(3) Range
(4) Restart/Exit
2
Here is the Mean 2.0Standard Devition is 0.8
Now I thought it might be an issue with how I'm calling each function, but the best I can tell thats not the case. Then I thought it might be a value that I didn't initialize, but it seems as though thats not it either. I just need another pair of eyes to see where I went wrong here.
#include <stdio.h>
#include <conio.h>
#include <math.h>
const int MAX_DATA=8;
void menu(float numbers[], int amount);
float mean(float numbers[],int amount);
float standard_dev(float numbers[], int amount);
float range( float numbers[], int amount);
int main()
{
int i=0, amount=0;
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=0; i<amount; i++)
{
printf("Please enter number %d\n", i+1);
scanf("%f",&numbers[i]);
}
menu(numbers,amount);
}
getch();
return 0;
}
void menu(float numbers[],int amount)
{
int input2=0;
printf("Statistical Calculator Menu");
printf("\n(1) Mean\n(2) Standard Deviation\n(3) Range\n(4) Restart/Exit\n");
scanf("%d",&input2);
if(input2==1)
{
mean(numbers,amount);
}
if (input2==2)
{
standard_dev(numbers,amount);
}
if (input2==3)
{
range(numbers,amount);
}
}
float mean(float numbers[],int amount)
{
int i;
float sum=0;
float average=0;
for (i=0; i<amount; i++)
{
sum=sum+numbers[i];
}
average=sum/amount;
printf("Here is the Mean %.1f", average);
return average;
}
float standard_dev(float numbers[], int amount)
{
float sdev=0,dev=0,sumsqr=0,variance=0;
int i;
float mean2=0;
mean2=mean(numbers,amount);
for (i=0; i<amount; i++)
{
dev=numbers[i]-mean2;
sumsqr+=dev*dev;
}
variance=sumsqr/(float)amount;
sdev=sqrt(variance);
printf("Standard Devition is %.1f", sdev);
return sdev;
}
float range(float numbers[],int amount)
{
int i;
float diff=0;
for (i=0; i<=amount; i++)
{
diff=numbers[amount]-numbers[1];
}
printf("%f\n",diff);
return diff;
}
float standard_dev(float numbers[], int amount)
{
float sdev=0,dev=0,sumsqr=0,variance=0;
int i;
float mean2=0;
mean2=mean(numbers,amount); // Here it is.
It calls the mean function, which actually prints something :) You can add boolean flag shouldPrint to functions and pass it as true when you want to print it.
Also, this problem is easily solvable with simple debugging your code...if actually looking at it doesn't seem to help...