1 / 8

Effective File Handling in MATLAB: Low-Level Input/Output Techniques

This guide covers low-level file input/output operations in MATLAB, focusing on commands like fopen, fclose, fprintf, and fscanf. You will learn how to open files for reading and writing in various formats (text or binary), handle errors for failed operations, and read/write formatted data efficiently. Examples are provided to illustrate how to create and manipulate data files, including generating sine and cosine tables. The guide is perfect for users needing robust control over file handling in MATLAB.

hinto
Télécharger la présentation

Effective File Handling in MATLAB: Low-Level Input/Output Techniques

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Low-level Input/Output • The load command does not always succeed in reading an input file. It only works when all lines in the file have the same ASCII format. Files with header material do not qualify, nor do binary files. • ASCII files that cannot be input with the loadfunction can be opened and input with MATLAB functions that are similar to C language functions. The MATLAB functions include fopen, fgets, fscanf, and sscanf.

  2. Low-level I/O Use to read files in any format • fopen: open a file • fclose: close a file • fread, fscanf: read from a file • fwrite,fprintf: write to a file • fgetl: read a line from file

  3. fopen Open a file and returns a file id reference to that file, returns -1 if file can’t be opened file_id = fopen(filename,permissions) - filename - name of the file to open - permissions - mode in which the file will be opened • ‘r’ - open file for reading • ‘w’ - writing • ‘a’ – append to existing file etc • Examples: To open a file for input is: infile_id = fopen('filename','r'); • The command to open a file for output is: outfile_id = fopen('filename','w');

  4. fclose • Close an open file status= fclose(file_id) • Status is 0 if the file was successfully closed, and -1 otherwise

  5. fprintf / fscanf • fprintf: write formatted data to a file fprintf(fid,format,val1,val2,....) • Example: fid = fopen('mydata.dat','wt'); fprintf(fid,'%f\n',pi); fprintf(fid,'%s\t%s\n',’hello’,’goodbye’); fclose(fid); • fscanf: read formatted data from a file array = fscanf(fid,format) • Example: fid = fopen('mydata.dat', 'rt'); p = fscanf(fid,'%f‘,1) h = fscanf(fid,’%s’,1) g = fscanf(fid,’%s’,1) fclose(fid);

  6. Write data example % open file fid = fopen('myfile.txt','wt');     % 'wt' means "write text" if (fid < 0)     error('could not open file "myfile.txt"'); end; % write some stuff to file for i=1:100     fprintf(fid,'%3d\t%6d\n',i,i*i); end; % close the file fclose(fid);

  7. Read data example % open file fid = fopen('myfile.txt','rt');     % 'rt' means "read text" if (fid < 0)     error('could not open file "myfile.txt"'); end; % read from file into table with 2 rows and 1 column per line tab = fscanf(fid,'%d %d\n',[2,inf]); % close the file fclose(fid);

  8. Exercises • Write a program to generate a table containing the sine and cosine of θ between 0o and 90o in 1o increments. Use a for loop and the fprintf function. The program should correctly label each of the columns in the table. • Write a program to read these numbers back into an n x 3 matrix using the fscanf function.

More Related