1. Data Files ELEC 206 Computer Applications for Electrical Engineers Dr. Ron Hayne

2. 206_C42 Data Files  Defining File Streams  Reading Data Files  Generating a Data File  Numerical Technique Linear Regression  Problem Solving Applied

3. 206_C43 File Stream Objects  File Stream Classes Derived from Stream Classes Input:ifstream Output:ofstream Header:fstream  Additional Member Functions open() fail() close()

4. 206_C44 ifstream Class  ifstream Object ifstream sensor1;  File Association sensor1.open("sensor1.dat");  Define and Initialize ifstream sensor1("sensor1.dat");  Error Checking if( sensor1.fail() )  File Input sensor1 >> t >> motion;

5. 206_C45 ofstream Class  ofstream Object ofstream balloon;  File Association balloon.open("balloon.dat");  Define and Initialize ofstream balloon("balloon.dat");  Append to Existing File balloon.open("balloon.dat", ios::app);

6. 206_C46 ofstream Class  Prompt for Filename string filename; cout << "Enter output filename"; cin >> filename; balloon.open(filename.c_str());  File Output balloon << time << ' ' << height << ' ' << velocity/3600 << endl;  Close File balloon.close();

7. 206_C47 Reading Data Files  Specified Number of Records Counter-controlled Loop  Trailer or Sentinel Signal Sentinel-controlled Loop  End of Data File End-of-file Loop

8. 206_C48 Specified Number of Records  sensor1.dat 10 0.0 132.5 0.1 147.2 0.2 148.3 0.3 157.3 0.4 163.2 0.5 158.2 0.6 169.3 0.7 148.2 0.8 137.6 0.9 135.9 sensor1.open(filename.c_str()); if(sensor1.fail()) { cout << "Error"; } else { sensor1 >> num_data_pts; for (k=1; k<=num_data_pts; k++) { sensor1 >> time >> motion;... }

9. 206_C49 Trailer or Sentinel Signals  sensor2.dat 0.0 132.5 0.1 147.2 0.2 148.3 0.3 157.3 0.4 163.2 0.5 158.2 0.6 169.3 0.7 148.2 0.8 137.6 0.9 135.9 -99 sensor2.open(filename.c_str()); if(sensor2.fail()) { cout << "Error"; } else { sensor2 >> time >> motion; do {... sensor2 >> time >> motion; } while (time >= 0);

10. 206_C410 End-of-File  sensor3.dat 0.0 132.5 0.1 147.2 0.2 148.3 0.3 157.3 0.4 163.2 0.5 158.2 0.6 169.3 0.7 148.2 0.8 137.6 0.9 135.9 sensor3.open(filename.c_str()); if(sensor3.fail()) { cout << "Error"; } else { sensor3 >> time >> motion; while ( !sensor3.eof() ) {... sensor3 >> time >> motion; }

11. 206_C411 Generating a Data File... #include... int main() {... string filename; ofstream balloon;... // Prompt user for name of output file. cout << "enter the name of the output file"; cin >> filename;

12. 206_C412 Generating a Data File // Open output file balloon.open(filename.c_str()); // Set format flags for file output. balloon << fixed << setprecision(2);... // Write data to file. balloon << setw(6) << time << setw(10) << height << setw(10) << velocity/3600 << endl;... // Close file and exit program. balloon.close(); return 0; }

13. 206_C413 Error Checking int ivar1, ivar2; cin >> ivar1 >> ivar2; while(!cin.eof)) { if(!cin) { cerr << "Error reading from standard input\n"; exit(1); } else { cout << ivar1 << ' ' << ivar2 << endl; cin >> ivar1 >> ivar2; }

14. 206_C414 Linear Regression  Determine the linear equation that is the best fit to a set of data points Least-squares Minimize sum of squared distances between line and data points y = mx + b

15. 206_C415 Problem Solving Applied  Ozone Measurements Problem Statement Use least-squares technique to determine a linear model for estimating ozone mixing ratio at a specified altitude Input/Output Description Linear Model Range of Altitudes zone1.dat

16. 206_C416 Problem Solving Applied Hand Example Alt(km) Ratio(ppmv) zone1.dat 20 3 24 4 26 5 28 6  n = 4  Σx = 98  Σy = 18  Σxy = 454  Σx 2 = 2436  m = 0.37  b = -4.6

17. 206_C417 Problem Solving Applied Algorithm Development Read data file values Compute sums and ranges Compute slope and y-intercept

18. 206_C418 Problem Solving Applied Algorithm Refinement Set count to zero Set sumx, sumy, sumxy, sumx2 to zero while not at end-of-file  read x, y  increment count  if count = 1, then set first to x  add x to sumx, y to sumy, xy to sumxy, x 2 to sumx2 set last to x compute m and b print first, last, m, b

19. /*----------------------------------------------------*/ /* Program chapter4_6 */ /* */ /* This program computes a linear model for a set */ /* of altitude and ozone mixing ratio values. */ #include using namespace std; int main() { // Declare and initialize objects. int count(0); double x, y, first, last, sumx(0), sumy(0), sumx2(0), sumxy(0), denominator, m, b; string filename("zone1.dat"); ifstream zone1;

20. // Open input file. zone1.open(filename.c_str()); if(zone1.fail()) cerr << "Error opening input file\n"; else { // Read and accumulate information. zone1 >> x >> y; while ( !zone1.eof() ) { ++count; if (count == 1) first = x; sumx += x; sumy += y; sumx2 += x*x; sumxy += x*y; zone1 >> x >> y; } last = x;

21. // Compute slope and y-intercept. denominator = sumx*sumx - count*sumx2; m = (sumx*sumy - count*sumxy)/denominator; b = (sumx*sumxy - sumx2*sumy)/denominator; // Set format flags cout << fixed << setprecision(2); // Print summary information. cout << "Range of altitudes in km: \n"; cout << first << " to " << last << endl << endl; cout << "Linear model: \n"; cout << "ozone-mix-ratio = " << m << " * altitude + " << b << endl; // Close file and exit program zone1.close(); } // end else system("PAUSE"); return 0; }

22. 206_C422 Problem Solving Applied Testing

23. 206_C423 Summary  Defining File Streams  Reading Data Files  Generating a Data File  Numerical Technique Linear Regression  Problem Solving Applied  End of Chapter Summary C++ Statements Style Notes Debugging Notes

24. 206_C424 Test #1 Review  Computer Hardware and Software  Engineering Problem-Solving Methodology  Program Structure  Simple C++ Constants and Variables C++ Operators Standard Input and Output Basic Functions

25. 206_C425 Test #1 Review  Structured Programming Algorithm Development Conditional Expressions Selection Statements Loops  Data Files Defining File Streams Reading Data Files Generating Data Files