Edit a column in a dat file with some header lines and a table

I want to change BlTwist column in the attached file by adding a constant floating or double number to each element of this column with the header lines preserved in the file. I have tried readtable and writetable functions and successfully changed the mentioned column but header lines vanish in the edited file. Only table remains with the changed column. I need header lines too. I couldn't upload the dat file so I converted it into a text file. Orignially, it has to have a dat extension.

[dpb]

You'll have to read and copy over the headerlines as text -- you can either do this with a loop and fgetl, fprintf and follow that with writing the data or you can read the full file as cellstr or string array and manipulate it in memory then write it back out.

MATLAB doesn't have a builtin facility to write more than the one header line as a package -- there are just too many possibilities to try to code for.

[Hashir Shafi]

Thanks for your comment. I have tried reading and copying the headerlines as text but then I don't know how to append the file with the manipulated table. And about second option, are you talking about storing all the content of the file in a cell array in workspace and then manipulating it? If yes, can you please give me an idea of how would you do it? Because I have tried doing it but couldn't succeed.

[ahmad hassan]

Hi Hashir,

I am searching solution for exact same problem. Did you find something about it?

Answer 1

[dpb]

A) goes something like

nHeaders=11;  % or whatever
fidi=fopen(filenameIn,'r');
fido=fopen(filenameOut,'w');
for i=1:nHeaders
  fprintf(fido('%s',fegts(fidi)))
end
data=textscan(fido(fmtInData));
...
%manipulate the data array here
fprintf(fido,fmtOut,data.')
fidi=fclose(fidi);
fido=fclose(fido);

B) would just

nHeaders=11;
data=importdata(filenameIn);  % will return cellstr() array
values=char(data(nHeaders+1:end));    % pick the data rows; convert to char() array
values=str2double(values);            % and convert to numeric
%manipulate the data as needed here
fido=fopen(filenameOut,'w');
for i=1:nHeaders
  fprintf(fido('%s',data{i})
end
fprintf(fido,fmtOut,values.')
fidi=fclose(fidi);
fido=fclose(fido);

You'll have to clean up the details and all, but gives the general sequence of operations. What you do with the embedded remark line in the file is going to be a tussle unless you can just ignore it with the 'CommentSyle' parameter with textscan on input. Otherwise, if you must echo it back out you'll have to parse the file as string data and locate it--the numeric conversion/reading routines will barf on it.

[Hashir Shafi]

Thanks for your input. I have already managed to write header lines in the new file. I am stuck at the manipulation part but I am working on it. Hopefully, it will be resolved soon.