Nov. 28, 2005 Lecture 14 - By Paul Lin 1 CPET 190 Problem Solving with MATLAB Lecture 14 Professor Paul Lin

Nov. 28, 2005 Lecture 14 - By Paul Lin 2 MATLAB Standard I/Os Standard I/Os Standard I/Os Standard input - keyboardStandard input - keyboard Standard output – monitor screenStandard output – monitor screen Standard error device – monitor screenStandard error device – monitor screen MATLAB I/Os MATLAB I/Os keyboard inputkeyboard input Filename = input(‘Enter a file name: ‘, ‘s’) Monitor outputMonitor output disp( ) function – display an array or text string fprintf( format,data) function – display data with desired format

Nov. 28, 2005 Lecture 14 - By Paul Lin 3 Lecture 14: File Input and Output MATLAB I/O Functions MATLAB I/O Functions diary( ) – save text of MATLAB sessiondiary( ) – save text of MATLAB session >> diary save( ) – save workspace variable to disksave( ) – save workspace variable to disk >> save FILENAME load( ) – load workspace variables from diskload( ) – load workspace variables from disk >> load FILENAME textread( ) – read formatted data from text filetextread( ) – read formatted data from text file

Nov. 28, 2005 Lecture 14 - By Paul Lin 4 Save and Load Function save function save function load function load function >> save 8_20_2004.mat >> clear >> whos >> load 8_20_2004.mat >> whos Name Size Bytes Class ans 1x1 8 double array x 1x1 8 double array y 1x1 8 double array Grand total is 3 elements using 24 bytes >> clear >> whos Current Directory

Nov. 28, 2005 Lecture 14 - By Paul Lin 5 MATLAB File Formats >>help filefomats Data formats Commands Returns MAT - MATLAB workspace load Variables in file. CSV - Comma separated numbers csvread Double array. DAT - Formatted text importdata Double array. DLM - Delimited text dlmread Double array. TAB - Tab separated textdlmreadDouble array. Spreadsheet formats Spreadsheet formats XLS - Excel worksheetxlsreadDouble array and cell array. WK1 - Lotus 123 worksheetwk1readDouble array and cell array. Scientific data formats Scientific data formats CDF - Common Data FormatcdfreadCell array of CDF records FITS - Flexible Image Transport System fitsreadPrimary or extension table data HDF - Hierarchical Data FormathdfreadHDF or HDF-EOS data set Movie formats Movie formats AVI - Movie avireadMATLAB movie.

Nov. 28, 2005 Lecture 14 - By Paul Lin 6 MATLAB File Formats >>help filefomats Data formats Command Returns Image formats TIFF - TIFF image imreadTruecolor, grayscale or indexed image(s). PNG - PNG imageimreadTruecolor, grayscale or indexed image. HDF - HDF imageimreadTruecolor or indexed image(s). BMP - BMP image imreadTruecolor or indexed image. JPEG - JPEG imageimreadTruecolor or grayscale image. GIF - GIF imageimreadIndexed image. PCX - PCX imageimreadIndexed image. XWD - XWD image imreadIndexed image. CUR - Cursor imageimreadIndexed image. ICO - Icon image imreadIndexed image. RAS - Sun raster image imreadTruecolor or indexed. PBM - PBM image imreadGrayscale image. PGM - PGM imageimreadGrayscale image. PPM - PPM imageimreadTruecolor image. Audio formats Audio formats AU - NeXT/Sun sound auread Sound data and sample rate. SND - NeXT/Sun sound auread Sound data and sample rate. WAV - Microsoft Wave sound wavread Sound data and sample rate

Nov. 28, 2005 Lecture 14 - By Paul Lin 7 MATLAB Low-Level File I/Os File Opening and Closing Functions File Opening and Closing Functions fopen( ) – open file for reading, writing, or appendingfopen( ) – open file for reading, writing, or appending fclose( ) – close file or filesfclose( ) – close file or files Binary I/O Binary I/O fread( ) – read binary data from filefread( ) – read binary data from file fwirte( ) – write binary data to filefwirte( ) – write binary data to file Formatted I/O Formatted I/O fscanf( ) – read formatted data from filefscanf( ) – read formatted data from file fprintf( ) – write formatted data to filefprintf( ) – write formatted data to file fgets( ) – read line from file, keep newline characterfgets( ) – read line from file, keep newline character fgetl( ) – read line form file, discard newline characterfgetl( ) – read line form file, discard newline character

Nov. 28, 2005 Lecture 14 - By Paul Lin 8 MATLAB Low-Level File I/Os (continued) String Conversion Functions String Conversion Functions sprinf( ) – write formatted data to stringsprinf( ) – write formatted data to string sscanf( ) – read string under format controlsscanf( ) – read string under format control File Positioning Functions File Positioning Functions ferros( ) – File I/O error statusferros( ) – File I/O error status feof( ) – test for end of filefeof( ) – test for end of file fseek( ) – set file position indicatorfseek( ) – set file position indicator ftell( ) – get file position indicatorftell( ) – get file position indicator frewind( ) – Rewind filefrewind( ) – Rewind file

Nov. 28, 2005 Lecture 14 - By Paul Lin 9 File Path Set File Path File -> Set Path -> Add Folder File -> Set Path -> Add Folder MTALAB Path Search -> G:\public_html\cpet190\ codes MTALAB Path Search -> G:\public_html\cpet190\ codes Click on Save button, and then Close button Click on Save button, and then Close button

Nov. 28, 2005 Lecture 14 - By Paul Lin 10 Example 14-1: Loading a Sequence of Data Files Create dataFiles Create dataFiles >> x = -10:0.1:10; >> y = 2*(x.^2) + 1; >> save dataFile1 >> clear y >> y = 2*(x.^2) + 10; >> save dataFile2 To open a sequence of enumerated data files To open a sequence of enumerated data files for file_no = 1: N fname = sprintf(‘testData%d’,file_no ); load(fname)end Create dataFiles Create dataFiles >> whos Name Size Bytes Class N 1x1 8 double array N 1x1 8 double array file_no 1x1 8 double array Fname 1x9 18 char array x 1x double array y 1x double array z 1x double array >> plot(x, y) >> plot(x, z)

Nov. 28, 2005 Lecture 14 - By Paul Lin 11 File Processing Reading a file Open a file for reading Open a file for reading Process reading from the file Process reading from the file Close the file Close the file Appending to a file Open a file for appending Open a file for appending Process appending the file Process appending the file Close the file Close the file Writing to a file Open a file for writing Open a file for writing Process writing to the file Process writing to the file Close the file Close the file

Nov. 28, 2005 Lecture 14 - By Paul Lin 12 Typical File Processing Open files Open files fid = fopen(' file_name ', permissions), where permissions can be one of the following: fid = fopen(' file_name ', permissions), where permissions can be one of the following: 'r‘ - Open the file for reading. The file must exist. An error occurs if the file does not exist.'r‘ - Open the file for reading. The file must exist. An error occurs if the file does not exist. 'r+‘ - Open the file for reading and writing. The file mut exist. An error occure if the file does not exist'r+‘ - Open the file for reading and writing. The file mut exist. An error occure if the file does not exist 'w‘ - Open the file for writing, create if necessary'w‘ - Open the file for writing, create if necessary 'w+‘ - Truncate or create for read and write'w+‘ - Truncate or create for read and write 'a‘ - Append (create if necessary)'a‘ - Append (create if necessary) 'a+ ‘ – Read and append (create if necessary)'a+ ‘ – Read and append (create if necessary) Write to, Read from files Write to, Read from files Close files Close files

Nov. 28, 2005 Lecture 14 - By Paul Lin 13 Example 14-2: Create a file - a table of the exponential function Pseudo Code 1. Create x and y vectors for exponential function 2. Open A File for Writing 3. Write Formatted Data – fprinf(fid, ‘format specifiers’, data) 4. Close File The program %save_exp.m x = 0:.1:1; y = [x' exp(x)']; fid = fopen('expfucntion.txt','w'); fprintf(fid,'%f %f\n', y); fclose(fid); File Content:

Nov. 28, 2005 Lecture 14 - By Paul Lin 14 Example 14-2: Create a file - a table of the exponential function  We edit the program as shown in previous slide  Set default directory or folder for storing the file  Debug or test the program through the MATLAB M-file editor  Open Windows Explorer and examine the created file

Nov. 28, 2005 Lecture 14 - By Paul Lin 15 Example 14-2: Create a file - a table of the exponential function  Open the expfunction.txt file using Microsoft Wordpad  Open the expfunction.txt file using Notepad

Nov. 28, 2005 Lecture 14 - By Paul Lin 16 Example 14-3: Reading Exponential Function File for Plotting %load_exp.m fid = fopen('expfucntion.txt','r'); % Retrieve data table a 11-by-2 [y1 count] = fscanf(fid,'%f', [11 2]); fclose(fid); % Extract first column x = y1(:,1) % Extract 2nd column exp_x = y1(:,2) plot(x, exp_x); grid on

Nov. 28, 2005 Lecture 14 - By Paul Lin 17 Example 14-4: Writing and Reading Binary Data %binary_file.m filename = input('Enter a file name: ', 's'); out_data = 100*rand(10, 1); [fid msg] = fopen(filename,'w'); % File open OK? if fid > 0 count = fwrite(fid, out_data, 'double'); count = fwrite(fid, out_data, 'double'); disp([int2str(count) ' value written to disk..']); disp([int2str(count) ' value written to disk..']); status = fclose(fid); status = fclose(fid);else % Failed to open the file % Failed to open the file disp(msg); disp(msg);end % Open the file for reading [fid msg] = fopen(filename, 'r'); if fid > 0 [in_data, count] = fread(fid, 10, 'double'); [in_data, count] = fread(fid, 10, 'double'); disp([int2str(count) ' value read from the disk..']); disp([int2str(count) ' value read from the disk..']); status = fclose(fid); status = fclose(fid);else % Failed to open the file % Failed to open the file disp(msg); disp(msg);endin_dataout_data

Nov. 28, 2005 Lecture 14 - By Paul Lin 18 Example 14-4: Writing and Reading Binary Data %binary_file.m filename = input('Enter a file name: ', 's'); out_data = 100*rand(10, 1); [fid msg] = fopen(filename,'w'); % File open OK? if fid > 0 count = fwrite(fid, out_data, 'double'); count = fwrite(fid, out_data, 'double'); disp([int2str(count) ' value written to disk..']); disp([int2str(count) ' value written to disk..']); status = fclose(fid); status = fclose(fid);else % Failed to open the file % Failed to open the file disp(msg); disp(msg);end % Open the file for reading [fid msg] = fopen(filename, 'r'); if fid > 0 [in_data, count] = fread(fid, 10, 'double'); [in_data, count] = fread(fid, 10, 'double'); disp([int2str(count) ' value read from the disk..']); disp([int2str(count) ' value read from the disk..']); status = fclose(fid); status = fclose(fid);else % Failed to open the file % Failed to open the file disp(msg); disp(msg);endin_dataout_data

Nov. 28, 2005 Lecture 14 - By Paul Lin 19 Example 14-4: Writing and Reading Binary Data in_data = out_data = Binary Files - Not Readable

Nov. 28, 2005 Lecture 14 - By Paul Lin 20 Summary MATLAB Standard I/Os - File Input and Output  Save and Load Function  MATLAB File Formats  MATLAB Low-Level File I/Os  File Path  File Processing Examples  Formatted Files  Binary Files Be sure to read Chapter 8 of the Text book, MATLAB help