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CPET 190

CPET 190. Problem Solving with MATLAB Lecture 14 Professor Paul Lin http://www.etcs.ipfw.edu/~lin. MATLAB Standard I/Os. Standard I/Os Standard input - keyboard Standard output – monitor screen Standard error device – monitor screen MATLAB I/Os keyboard input

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CPET 190

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  1. CPET 190 Problem Solving with MATLAB Lecture 14 Professor Paul Lin http://www.etcs.ipfw.edu/~lin Lecture 14 - By Paul Lin

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

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

  4. Save and 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 • save function • load function Current Directory 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 text dlmread Double array. Spreadsheet formats XLS - Excel worksheet xlsread Double array and cell array. WK1 - Lotus 123 worksheet wk1read Double array and cell array. Scientific data formats CDF - Common Data Format cdfread Cell array of CDF records FITS - Flexible Image Transport System fitsread Primary or extension table data HDF - Hierarchical Data Format hdfread HDF or HDF-EOS data set Movie formats AVI - Movie aviread MATLAB movie. Lecture 14 - By Paul Lin

  6. MATLAB File Formats >>help filefomats Data formats Command Returns Image formats TIFF - TIFF image imread Truecolor, grayscale or indexed image(s). PNG - PNG image imread Truecolor, grayscale or indexed image. HDF - HDF image imread Truecolor or indexed image(s). BMP - BMP image imread Truecolor or indexed image. JPEG - JPEG image imread Truecolor or grayscale image. GIF - GIF image imread Indexed image. PCX - PCX image imread Indexed image. XWD - XWD image imread Indexed image. CUR - Cursor image imread Indexed image. ICO - Icon image imread Indexed image. RAS - Sun raster image imread Truecolor or indexed. PBM - PBM image imread Grayscale image. PGM - PGM image imread Grayscale image. PPM - PPM image imread Truecolor image. 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 Lecture 14 - By Paul Lin

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

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

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

  10. Example 14-1: Loading a Sequence of Data Files • Create dataFiles >> whos Name Size Bytes Class N 1x1 8 double array file_no 1x1 8 double array Fname 1x9 18 char array x 1x201 1608 double array y 1x201 1608 double array z 1x201 1608 double array >> plot(x , y) >> plot(x, z) • 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 for file_no = 1: N fname = sprintf(‘testData%d’,file_no); load(fname) end Lecture 14 - By Paul Lin

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

  12. Typical File Processing • Open files • 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 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+‘ - Truncate or create for read and write • 'a‘ - Append (create if necessary) • 'a+ ‘ – Read and append (create if necessary) • Write to, Read from files • Close files 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: 0 1.0000 0.1000 1.1052 0.2000 1.2214 0.3000 1.3499 0.4000 1.4918 0.5000 1.6487 0.6000 1.8221 0.7000 2.0138 0.8000 2.2255 0.9000 2.4596 1.0000 2.7183 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 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 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 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'); disp([int2str(count) ' value written to disk ..']); status = fclose(fid); else % Failed to open the file disp(msg); end % Open the file for reading [fid msg] = fopen(filename, 'r'); if fid > 0 [in_data, count] = fread(fid, 10, 'double'); disp([int2str(count) ' value read from the disk ..']); status = fclose(fid); else % Failed to open the file disp(msg); end in_data out_data 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'); disp([int2str(count) ' value written to disk ..']); status = fclose(fid); else % Failed to open the file disp(msg); end % Open the file for reading [fid msg] = fopen(filename, 'r'); if fid > 0 [in_data, count] = fread(fid, 10, 'double'); disp([int2str(count) ' value read from the disk ..']); status = fclose(fid); else % Failed to open the file disp(msg); end in_data out_data Lecture 14 - By Paul Lin

  19. Example 14-4: Writing and Reading Binary Data in_data = 95.0129 23.1139 60.6843 48.5982 89.1299 76.2097 45.6468 1.8504 82.1407 44.4703 out_data = 95.0129 23.1139 60.6843 48.5982 89.1299 76.2097 45.6468 1.8504 82.1407 44.4703 Binary Files - Not Readable 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 Lecture 14 - By Paul Lin

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