How to write to an existing column of a file?

Hey there,

I have a .daf file here (you can open in wordpad) and you can see that there are 10 columns. I want to overwrite just the sixth column with number 1 (they're all 0's but in some rows I want to put 1). Like say on the 100th, 200th, 300th rows, I want to make them 1. I also want to save it in the same file.

How can I do that? Can someone help me?

Thank you!

Answer 1

[per isakson]

AJ739_20170127115441_v2.daf is an UTF-8 encoded text file according to Notepad++.

It's close to impossible to overwrite a column in a text file.

You have to read the file and write a new file (or overwrite the old) with modified data.

In response to comments

See Import Text Data Files with Low-Level I/O

There are many ways. This outlines a simple one.

fid_in  = fopen( 'AJ739_20170127115441_v2.daf', 'r' );
fid_out = fopen( 'any_name_and_remane_later.txt', 'w+' );
str = 'anything';
while not( strcmp( str, '"***Data start***"' ) )
    str = fgetl( fid_in );
    fprintf( fid_out, '%s\n', str ); 
end
cac = textscan( fid_in, '%d...%q', 'Delimiter',',' )
fclose( fid_in )
...
fclose( fid_out )

Read about UTF-8 in the help on fopen

I'm not sure I understand "I want to overwrite just the sixth column with number 1 (they're all 0's but in some rows I want to put 1). Like say on the 100th, 200th, 300th rows, I want to make them 1." The sixth column of the uploaded file contains only zeros.

The code below writes a modified file with tab-delimited data.

fid_in  = fopen( 'AJ739_20170127115441_v2.daf', 'r' );
fid_out = fopen( 'any_name_and_remane_later.txt', 'w+' );
str = 'anything';
while not( strcmp( str, '"***Data start***"' ) )
    str = fgetl( fid_in );
    fprintf( fid_out, '%s\n', str ); 
end

0,0,0,0,0,0,0,0,0,"(0)[0.00/ 0]" 252502,49,1,0,0,0,0,0,0,"Respiratory Level Error.(0)[1.87/ 488]"

cac = textscan( fid_in, '%d%d%d%d%d%d%d%d%d%q'      ...
            ,   'Delimiter',',', 'CollectOutput',true );
fclose( fid_in );
my_data = cac{1};
str = cac{2};

The 6th column contains only zeros; all(my_data(:,6)==0) returns true

my_data(:,6) = 1;   
for jj = 1 : size(my_data,1)
    fprintf( fid_out, '%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\t"%s"\n'  ...
                    , my_data(jj,:), str{jj}                        );
end
fclose( fid_out );
disp('Done!')

See tprintf writes tabular data to a text file

[Kash Costello]

Hi! Do you know how I can write my data with tabs in between? There are also the first 31 lines that I am not sure how to write into another file :(

[per isakson]

See addendum in my answer.

[Kash Costello]

I saw! Thanks! What about writing the 10 columns below the string characters? I've been trying to figure that out but I don't know how to write them >.<