259201 Computer Programming for Engineers

1. 259201Computer Programmingfor Engineers Basic Programming II

2. Outline • Standard Deviation Function (SD) • Complex Guessing Game

3. Standard Deviation (SD) • For the group of data, the standard deviation measures the spread of the data. • Given a set of data • the standard deviation (SD) is calculated as

4. Standard Deviation (SD) • the procedure to compute the SD • 1. Obtain the data, • 2. Compute the average, • 2. Compute the sum , • 3. Compute the SD,

5. Standard Deviation (SD): Accepting Data Task1: Obtain the set of data • Store 10 scores from the user in variable a[0], a[1], ...,a[9] #include <stdio.h> voidmain() { int a[10],n; for ( n=0 ; n<10 ; n++ ) { printf("Enter your data:"); scanf("%d", &a[n]); } }

6. Standard Deviation (SD) • Task 2 Compute the average, #include <stdio.h> voidmain() { int a[10], n; float csum = 0, avg; for ( n=0 ; n<10 ; n++ ) { printf("Enter your data:"); scanf("%d", &a[n]); csum = csum + a[n]; } avg=csum/10.; } Question 1. What happens when we do not define csum=0 ?

7. Standard Deviation (SD) • Task 3. Compute the sum of the square of the difference between the data and the average. • This can be done using pow function pow((a[0]-avg),2)

8. Standard Deviation (SD) • Task3. Continued • Store the sum in the variable, sq_sum ... #include <math.h> ... float sq_sum=0; ... for ( n=0 ; n<10 ; n++ ) { sq_sum = sq_sum + pow((a[n]-avg),2); }

9. Standard Deviation (SD) • Task 4: Divide it by 10 and the take the square root to complete the SD. ... #include <math.h> ... float sq_sum = 0, sd; ... for ( n=0 ; n<10 ; n++ ) { sq_sum = sq_sum + pow((a[n]-avg),2); } sd=sqrt(sq_sum/10);

10. Standard Deviation (SD) • SD #include <stdio.h> #include <math.h> void main() { float csum=0, avg, sq_sum=0, sd; int a[10], n; //get data and compute avg for ( n=0 ; n<10 ; n++ ) { printf("Enter your data:"); scanf("%d", &a[n]); csum = csum + a[n]; } avg=csum/10; //compute SD for ( n=0 ; n<10 ; n++ ) { sq_sum = sq_sum + pow((a[n]-avg),2); } sd=sqrt(sq_sum/10); printf(“SD = %.2f\n”, sd); }

11. Grade Assigning using SD • Once the SD has been computed, it can be used to assign the grade for each of the score.

12. Guessing Game (Again) #include <stdio.h> #include <stdlib.h> #include <time.h> void main() { int n, g, i = 1; srand(time(NULL)); n = rand() % 11; // generate a random number 0-10 do { printf("Guess a number[0,10]:"); scanf("%d", &g); i++; } while ((g!=n)&&(i<=5)); if (g == n) printf(“You got it.\n”); else printf("You failed. Please try again.\n"); } • Previously on the Guessing game.

13. Guessing Game (Again) • Improve the guessing game so that it tells if the right answer is greater than the guess or less than the guess. Guess a number[0,10]:2 Greater than this. Guess a number[0,10]:6 Less than this. Guess a number[0,10]:5 You got it.

14. Guessing Game (Again) • The random number (answer) is stored in variable n • n • The guess is stored in variable g • g

15. g==n g>n display ‘You got it.’ display ‘Less than this.’ display ‘Greater than this.’ Guessing Game (Again) • Flowchart showing the relationship between the guess and the number. • {g==n You got it, g>n less than this, g < n greater than this} N N Y Y

16. Guessing Game (Again) • According to the flowchart, the translation into code is if (g==n) { printf("You got it.\n"); } else if (g>n) { printf("Less than this.\n"); } else { printf("Greater than this.\n"); }

17. #include <stdio.h> #include <stdlib.h> #include <time.h> void main() { int n, g, i = 1; srand(time(NULL)); n = rand() % 11; // generate a random number 0-10 do { printf("Guess a number[0,10]:"); scanf("%d", &g); if (g==n) { printf("You got it.\n"); } else if (g>n) { printf("Less than this.\n"); } else { printf("Greater than this.\n"); } i++; } while ((g!=n)&&(i<=5)); if (g != n) printf("You failed. Please try again.\n"); }

18. Summary • Using flowchart can help us on planning the program; • When you cannot see the solution right away, break the problem into smaller pieces and solve one at a time.