Replacing elements of a text file

Dear community, i already searched for my matter but i do not find any good reply. Btw, i have a text file "map.txt" composed by different letters in a 25x60 matrix.

And i need to rewrite this matrix in a new text file replacing all the letters different from "i" with an "e" (it's an academic exercise). I really have different difficulties loading the file.

My idea was using some code like this one:

filename='mappa.txt';
delimiterIn='';
headerlinesIn=25;
A=importdata(filename,delimiterIn,headerlinesIn);

[n,m]=size(A);
Aout=zeros(size(A));

for i=1:n
    for j=1:m
       if (A(i,j)==('I'))
           Aout(i,j)=('X');
       else
           Aout(i,j)=('~');
       end
    end
end

disp=(Aout)

but it obviously doesn't work. Any suggestion? Kindly, A.

[dpb]

importdata is for numeric, not character data.

Would need sample of the file to know precisely the input, but to do a simple character substitution, look at

doc strrep

[Alberto Rizzo]

just resolved using

      while ~feof(fin)
          s=fgetl(fin);
          m=size(s,2);
          for i=1:m
             if (s(i)==a) 
                 s(i)=('X');
             else
                 s(i)=('~');
             end
          end 
          disp(s);
          fprintf(fout,'%s\n',s);

thanks for ur reply

Answer 1

[Stephen23]

This is easy to do using some simple commands:

>> str = fileread('mappa.txt');
>> idx = str~='i' & isstrprop(str,'alpha');
>> str(idx) = 'e';
>> fid = fopen('newfile.txt','w');
>> fprintf(fid,'%s',str);
>> fclose(fid);

Where the original file looks like this:

qwert
yuiop
uoiow
iupwo

and the newfile looks like this:

eeeee
eeiee
eeiee
ieeee

I had to invent my own data because you did not provide us with any test-file for us to test our code with. If you attach your data in a comment then we can check that it works properly with your data too.

Note that I assumed that the file contains only alphabetic characters. Your final algorithm depends on what you mean by "all the letters different from "i"": for example the newline character is different from i, should this also be replaced by e? You can adjust this behavior by changing the isstrprop category string.

[Alberto Rizzo]

I'm really sorry for this. As i already said, i'm a newbie of this community. I'll provide something more detailed next time.

Btw, i really never read anything about isstrprop. The file contains only alphabetic characters; i'll try rewriting my code asap.

Thanks for your time.

[Stephen23]

If "The file contains only alphabetic characters", then how can it be arranged in a matrix without any newline characters?