Write Data to Text Files in MATLAB

In MATLAB, there is a built-in function “fprintf()” that is used to write data to a text file. The best part of this function is that it writes formatted data to a text file exactly in the same way as specified.

Syntax

fprintf(fileID, FormateSpecifier, Variables);

Format Specifiers in MATLAB

The following table gives a list of different format specifiers used with the “fprintf()” function in MATLAB:

S. No.	Format Specifier	Description
1.	%d or %i	Display a value as an integer.
2.	%f	Display floating point number.
3.	%s	Display a string array or a character vector.
4.	%e	Display values in exponential notation.
5.	%c	Display a single character.
6.	%g	Display values with no trailing zeros.

Escape Sequences in MATLAB

The following table gives a list of different escape sequences used with the “fprintf()” function in MATLAB:

S. No.	Escape Sequence	Description
1.		To create a new line.
2.	\t	To insert a horizontal tab space.
3.	\v	To insert a vertical tab space.
4.	\r	Carriage return.
5.	\	Backslash
6.	\b	Backspace
7.	\f	Form feed
8.	%%	Percentage character
9.	\a	Alarm
10.	''	Single quotation mark

Algorithm

Step 1-  Store your data in a variable or variables.

Step 2 - Open a file for writing data into it. For this use the “fopen()” function.

Step 3 - Check if the file was successfully opened. If not, then throw an error message. For this compare the file identifier with -1.

Step 4 - Write the data to the text file. For this use the “fprintf()” function.

Step 5 - Close the file to free up system resources. For this use the “fclose()” function.

Step 6 - Display a process completion message to the user.

Now, let us understand the process of writing up data to a text file in MATLAB with the help of a few example programs.

Example

% A MATLAB program to write multiple numeric values to a 
text file.
% Create a sample array of integers. 
x = [10 20 30 40 50; 100, 200, 300, 400, 500; 1000, 2000, 
3000, 4000, 5000];
% Open the file for writing
file1 = fopen('TextFile1.txt', 'w');
% Check if the file was successfully opened
if file1 == -1
   error('Failed to open the file.');
end
% Write data to the text file
   fprintf(file1, '%d %d %d 
', x);
% Close the file to free up system resources
fclose(file1);
disp('Data has been written to the text file.');

Output

Data has been written to the text file.

View the content of the text file by compiling the following statement:

disp('Data in the File:');
type TextFile1.txt;

Explanation

In this MATLAB program, we have created an array “x” containing integers. We want to write this data to a text file named “TextFile1.txt”.

For this, first we call “fopen” function with “w” as the access mode to open the file in write mode. To refer the opened file, we use a file identifier “file1”. Then, we check the file for successful opening, if the file is opened, an error message is shown. After that we call “fprintf” function with “%d” as format specifier to write the integer data to the text file. Then, we call “fclose” function to close the file to free up the resources. Finally, we display a message to inform that the data is successfully written to the file.

Also, to view the data written to the file, we execute a statement “type TextFile1.txt”.

Example

% A MATLAB program to write floating point numeric values to a text 
file.
% Create a sample array of floating point numbers. 
x = [10.25 20.52 30.56 40.45 50.65; 100.552, 200.235, 300.563, 
400.456, 500.256; 1000.4256, 2000.2356, 3000.2356, 4000.2563, 
5000.2356];
% Open the file for writing
file2 = fopen('FloatingPoint.txt', 'w');
% Check if the file was successfully opened
if file2 == -1
   error('Failed to open the file.');
end
% Write data to the text file
   fprintf(file2, '%f %f %f 
', x);
% Close the file to free up system resources
fclose(file2);
disp('Data has been written to the text file.');

Output

Data has been written to the text file.

View the content of the text file by compiling the following statement:

disp('Floating Point Numbers in the File:');
type FloatingPoint.txt;

Explanation

In this MATLAB program, we have created an array “x” containing floating point numbers. We want to write this data to a text file named “FloatingPoint.txt”.

For this, we call “fopen” function with “w” as the access mode to open the file in write mode. To refer the opened file, we use a file identifier “file2”. Then, we check the file for successful opening, if the file is opened, an error message is shown. After that we call “fprintf” function with “%f” as the format specifier to write the data to the text file. Then, we call “fclose” function to close the file to free up the resources. Finally, we display a message to inform that the data is successfully written to the file.

To view the data written to the file, we execute a statement “type FloatingPoint.txt”.

Example

% A MATLAB program to write a string of text to a text file.
% Create a sample string of text. 
x = 'Tutorials Point is a Best Online Platform to Learn Coding.';
% Open the file for writing
file3 = fopen('MyFile.txt', 'w');
% Check if the file was successfully opened
if file3 == -1
   error('Failed to open the file.');
end
% Write data to the text file
   fprintf(file3, '%s', x);
% Close the file to free up system resources
fclose(file3);
disp('Data has been written to the text file.');

Output

Data has been written to the text file.

View the content of the text file by compiling the following statement:

disp('String in the text file is ');
type MyFile.txt;

Example

% A MATLAB program to write data to a text file using a 
mathematical expression.
% Create sample numeric data. 
x = 1:10;
% Specify a mathematical expression
y = [x; x.^3];
% Open the file for writing
file4 = fopen('cubepower.txt', 'w');
% Check if the file was successfully opened
if file4 == -1
   error('Failed to open the file.');
end
% Write data to the text file
   fprintf(file4, '%s \t \t %s 
', 'x', 'cube');
   fprintf(file4, '%f \t %f 
', y);
% Close the file to free up system resources
fclose(file4);
disp('Data has been written to the text file.');

Output

Execute the following code to get the result:

type cubepower.txt;

Example

% A MATLAB program to write a hyperlink to a text file.
% Specify the website url.
url = 'https://www.tutorialspoint.com/index.htm';
% Specify the name of the website
website = 'Tutorials Point';
% Open the file for writing
file5 = fopen('tutorialspoint.txt', 'w');
% Check if the file was successfully opened
if file5 == -1
   error('Failed to open the file.');
end
% Write the hyperlink to the text file
   fprintf(file5, ' "%s"  
', url, website);
% Close the file to free up system resources
fclose(file5);
disp('Data has been written to the text file.');

Output

Execute the following code to get the result:

type tutorialspoint.txt;

Conclusion

This is all about writing data to a text file in MATLAB. The above MATLAB programs illustrate the implementation of “fprintf()” function in MATLAB to write data to a text file.