how to remove this error please some one help me

 Error in load_database (line 9)
        cd(strcat('att_faces',num2str(i)));

Answer 1

[Walter Roberson]

The code is expecting to be able to change directory to a subdirectory directly under the current one, with the subdirectory named att_faces followed by a number with no leading zeros. Either that directory is missing or else you started running the code from the wrong folder or else the code is forgetting to cd() back to the original directory before trying to cd() again.