I get an undefined error when compiling this. Everything else works when I take out the standard deviation, but I get the error when I put it back in.

I also need help with the user input. My professor wants it done in a certain way and I just can't figure out how it's done. This is just an example of the output.

Enter Number:

1.0 5.5 2.9 -1

After that, the program is suppose to count how many integers there are and calculate the rest of the stuff. -1 is there to tell the program to not count the numbers beyond it.

One more thing. I can't find out why the loop isn't working in at the end. When I answer "y" it just prints back the summary instead of going back to the beginning asking "Enter number." I did it similar to her notes and it still doesn't work.

Thanks.

Code:#include <stdio.h> #include <math.h> int main(void) { double a; int n = 0; char answer; double max = 0; double min = 9999; double sum = 0; double vsum; double mean = 0; double vari = 0; double devi = 0; do { while(a != -1) { printf("Enter numbers: \n"); scanf("%lg",&a); if (a != -1) { n++; if (a >= max) max = a; if (a <= min) min = a; sum += a; vsum += a * a; } } mean = sum / n; vari = (vsum / n) - (mean * mean); devi = sqrt(vari); printf("You entered %i numbers \n", n); printf("Maximum value entered: %g \n", max); printf("Minimum value entered: %g \n", min); printf("Sum of all the values read: %g \n", sum); printf("Mean of all values: %g \n", mean); printf("Variance of all values: %g \n", vari); printf("Standard Deviation of all values: %g \n", devi); printf("\nWould you like to factor another (Y/N)? "); scanf(" %c",&answer); } while (answer!='N'); return 0; }