How to save Matrix in text-file using format double?

I like to save a matrix into a textfile.

save('name','matrix','-ascii') saves matrix in a format

1.93e3 1.32e-2

1.94e3 1.03e-3

but I need:

1930 0.0132

1940 0.00103

How to manage?

Answer 1

[Stephen23]

Using SAVE for text files is very outdated. The recommended approach is to e.g. WRITEMATRIX:

M = [1930,0.0132; 1940,0.00103];
writematrix(M,'mytest.txt')

Checking

type mytest.txt

1930,0.0132
1940,0.00103

[Holger]

Thanks, that helped me!

Answer 2

[Umar]

Hi @Holger,

You can use the fprintf function instead of save. The fprintf function allows for greater control over the formatting of the output. For more guidance on this function, please refer to

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

Here is how you can do it:

Prepare Your Matrix: Ensure that your matrix is defined in MATLAB.

   matrix = [1.93e3, 1.32e-2; 1.94e3, 1.03e-3];

Open a File for Writing: Use the fopen function to create or open a text file where you want to save your data.

   fileID = fopen('output.txt', 'w'); % Open file for writing

Format and Write Your Data: Use fprintf to write the data into the file in your desired format. You can specify the format string to ensure that numbers are represented as you wish (fixed-point).

   fprintf(fileID, '%.0f %.4f\n', matrix'); 
   % Transpose matrix for correct orientation

In this example:

%.0f formats the first column as an integer.

%.4f formats the second column with four decimal places.

Close the File: After writing, always close the file to ensure all data is saved properly.

   fclose(fileID);

Here is how your complete MATLAB code would look:

% Define your matrix
matrix = [1.93e3, 1.32e-2; 1.94e3, 1.03e-3];

% Open a text file for writing
fileID = fopen('output.txt', 'w');

% Write the matrix to the file in the desired format
fprintf(fileID, '%.0f %.4f\n', matrix');

% Close the file
fclose(fileID);

Please see attached.

Using fprintf gives you flexibility not only in formatting but also in controlling how many digits appear after the decimal point and whether numbers are displayed in fixed-point or scientific notation. By following these steps, you should be able to save your matrix in MATLAB exactly as you require!

Hope this helps.

[Holger]

Hi @Umar

thanks a lot, that helps me!

best regards

Holger

[Umar]

Hi @Holger,

Thank you for your kind words. I am pleased to hear that the information provided was helpful to you. If you have any further questions or need additional assistance, please do not hesitate to reach out.