Save data to .txt file

How do I save data to a txt file? I want to create a simple two column text file, where the first column is the data from an nx1 matrix and the second column is a different n x 1 matrix. I also want column headings in the first row of each column.

thanks

[Raghunandan V]

the problem is you are trying to store them in an array whereas you have to store them in a cell array since each file is of different size Try this code

fileName={'new1.txt', 'new2.txt', 'new3.txt'};
%open file identifier
fid=fopen('MyFile.txt','w');
for k=1:length(fileName)
    %read the file name as string including delimiters and next lines
    List=textread(fileName{1,k},'%s','delimiter','\n');
    %arrange them in order of k if you want in a cell array
    FinalList{k,1}=List;
    %or print them into a file.
    fprintf(fid, [cell2mat(List)  '\n']);
end
%close file indentifier
fclose(fid)

Answer 1

[José-Luis]

To write a text file with columns of data that have variable names, use the “writetable” function. First, create the data to write, put it in a table with variable names, and then write the data to text file.

% Create two columns of data
A  = rand(10,1);
B = rand(10,1);

% Create a table with the data and variable names
T = table(A, B, 'VariableNames', { 'A', 'B'} )

% Write data to text file
writetable(T, 'MyFile.txt')

For more information see:

https://www.mathworks.com/help/matlab/ref/writetable.html

Starting in R2019a, you can use "writematrix" to write a matrix to a file.

For example:

M=magic(5);
writematrix(M, "M.txt");

For more information on "writematrix", please refer to the following documentation:

https://www.mathworks.com/help/releases/R2019a/matlab/ref/writematrix.html

[Bernoulli Lizard]

When I to open this file [in Notepad] the format is messed up. Instead of displaying in two columns, it is one long string. How can I make it display as two columns?

[Azzi Abdelmalek]

open it with wordpad

[José-Luis]

You just discovered one of the joys of moving files between Unix and Windows: the end-of-line is not the same

http://www.linuxforums.org/forum/miscellaneous/112428-new-line-character-windows-linux.html

Since you use windows, it should work with:

fprintf(fid, '%d %d \r\n', [A B]);

Note that you would also need to modify the first fprintf. Also, notepad is evil.

[Bernoulli Lizard]

After doing this the data appears to be displayed in two separate columns, but the data is completely jumbled. Some of the x data is in the y column and vice versa. This happens whether I open it in wordpad or in notepad.

[José-Luis]

My bad, %d is the format for integers, you probably want to save floats. If your data are floats, then:

fprintf(fid, '%f %f \r\n', [A B]);

For more info on formats:

doc fprintf

[Bernoulli Lizard]

That allows it to display more sig figs, but the data is still in the wrong order. It is displaying all of the x data in both columns, and then all of the y data in both columns.

So instead of

1 10

2 20

3 30

4 40

5 50

it is saving it as

1 2

3 4

5 10

20 30

40 50

I have no idea why it would do this or how to fix it.

[José-Luis]

This should work, taking the transpose so the data is in the proper order:

A  = (1:10)';
B = (10:10:100)';
header1 = 'Hello';
header2 = 'World!';
fid=fopen('MyFile.txt','w');
fprintf(fid, [ header1 ' ' header2 '\r\n']);
fprintf(fid, '%f %f \r\n', [A B]');
fclose(fid);

[Eric]

Is it possible your data are 1xn rather than nx1? Try this:

fprintf(fid, '%f %f \n', [A(:) B(:)]);

A(:) converts the matrix A into a column vector (which is what you want assuming A is indeed a vector).

Good luck,

Eric

[Bernoulli Lizard]

Wow, I never thought of just transposing [A B].

Thank you, you're brilliant!

[José-Luis]

No worries. I am not so sure about the brilliant part, but I'll make sure to tell my supervisor. :)

[swati khan]

 % code
A  = rand(10,1);
B = rand(10,1);
header1 = 'Hello';
header2 = 'World!';
fid=fopen('MyFile.txt','w');
fprintf(fid, [ header1 ' ' header2 'r\n']);
fprintf(fid, '%f %f r\n', [A B]');
fclose(fid);true
    % code

Thanks for the code. Was looking for something exactly like this. May I add that "If you plan to read the file with Microsoft® Notepad, use '\r\n' instead of '\n' to move to a new line." https://www.mathworks.com/help/matlab/ref/fprintf.html

[lafnath p]

how to get the size of data in file

[celine azizieh]

Better to use: fid=fopen('MyFile.txt','wt');

instead of fid=fopen('MyFile.txt','w');

otherwise when opening the file with notepad, there is not return to the line... everything is written on one line.

Answer 2

[WAEL Al-dulaimi]

In case I want to open a text file and I have a loop that each time give me different results {x1, x1...xn}. So how can I save all the data that I got from the loop in different names such as y1, y2 .... etc? And under each one of them, I can find the result that I got. I'll appreciate your help. thank you

[Peter]

It is unclear form your question what you are trying to loop across. It sounds like your trying to read from a single text file; is this true? In any case you should be able to just assign the value that you read to a new variable. If you know how long each data set is you can preallocate matrices for those variables, but that's not necessarily necessary.

Answer 3

[Ahmed Saeed Mansour]

How can we save transient CFD results in a file during running the code?

Answer 4

[Paige Kierce]

randA