how to extract certain lines from a csv file

Hi everyone, I really need a hand. I have a csv file containing many lines which cannot be opened in excel. I would like to create a script that allows me to keep the first line and then go and read the file line by line.

Now each line is made up of several characters, at a certain point in the line there is the element that identifies me what that line refers to (eg: UPRE_S14SPLO_901), in total there are 21 of these elements. I would like the mi script to read each line and create 21 csv files corresponding to the elements that interest me where all the lines referring to that element are contained.

Does anyone know how to do? I am attaching an example of the file to make you understand how it is structured.

Answer 1

[Mathieu NOE]

hello Giuseppe !

here you are ... I converted the prova.xlsx into csv file first to be coherent with the assumption we are working with csv data

the code is below

enjoy it :

Filename = 'prova.csv';
string = 'UPRE_S14SPLO_901';
% string = 'UPRE_S14SPLO_902';

output_matrix = retrieve_csv2(Filename,string)

% % save the output to one single csv file
% output_file = 'out_prova_all.csv';
% writecell(output_matrix,output_file);


% save the output to individual csv file (title + 1 line of data)
[m,n] = size(output_matrix);
title_line = output_matrix{1,:};

for ci = 2:m
    output_file = ['out_prova_ind' num2str(ci-1) '.csv'];
    data_line = output_matrix{ci,:};
    simple_output_matrix{1,:} = title_line;     % title line (always the same)
    simple_output_matrix{2,:} = data_line;    % data line (increment)
    writecell(simple_output_matrix,output_file);
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function output_matrix = retrieve_csv2(Filename,string)

fid = fopen(Filename);

tline = fgetl(fid);

k = 1;
output_matrix{1,1} = tline;

while ischar(tline)

    check = strfind(tline,string);
    
    if ~isempty(check)
        
        k = k+1;    % loop over line index
        output_matrix{k,:} = tline;

    end
   
tline = fgetl(fid);
    
end

fclose(fid);

[Giuseppe D'Amico]

hi mathieu thank you for your answer, the script works, however I get an error; also I would like to ask you, the data that I have in output how can I save them in a csv file?

[Mathieu NOE]

hello Giuseppe

which matlab release are you using ? I have R2020b

the function that creates the error on your side is writecell which I believe appeared in 2018

I tested some alternatives , so replace the line that creates the error

so replace :

writecell(simple_output_matrix,output_file);

with one of the following options :

xlswrite(output_file,simple_output_matrix);% Matlab R2000 and above

or as an ascii format txt (works also with csv or txt file extension). I have put the function saveascii in attachement

saveascii(simple_output_matrix,output_file)  % keep csv file format output
saveascii(simple_output_matrix,'test.txt')   % export as simple txt file (quite the same)

[Mathieu NOE]

one more possible alternative is :

dlmwrite(output_file, char(simple_output_matrix),'delimiter',''); % ok