How to Use textscan in MATLAB for Reading Text Data

Use textscan in MATLAB to read formatted data from text files or strings by specifying a file identifier and a format string. It returns data in cell arrays, allowing easy extraction of different data types from mixed content.

Syntax

The basic syntax of textscan is:

• C = textscan(fileID, formatSpec) reads data from an open file.
• C = textscan(fileID, formatSpec, N) reads N times according to the format.
• C = textscan(fileID, formatSpec, Name, Value) uses additional options like delimiters.

Here, fileID is the file handle from fopen, formatSpec defines the data types to read, and C is a cell array with the parsed data.

matlab

fileID = fopen('data.txt','r');
data = textscan(fileID, '%s %d %f');
fclose(fileID);

Example

This example reads a text file with three columns: a string, an integer, and a floating-point number. It shows how textscan parses mixed data types into separate cells.

matlab

fileID = fopen('example.txt','w');
fprintf(fileID, 'John 25 72.5\nAnna 30 65.2\nMike 22 80.1\n');
fclose(fileID);

fileID = fopen('example.txt','r');
data = textscan(fileID, '%s %d %f');
fclose(fileID);

names = data{1};
ages = data{2};
weights = data{3};

disp(names);
disp(ages);
disp(weights);

Output

    'John'
    'Anna'
    'Mike'

    25
    30
    22

   72.5000
   65.2000
   80.1000

Common Pitfalls

Common mistakes when using textscan include:

• Not opening the file before reading or forgetting to close it after.
• Using incorrect format specifiers that don't match the data.
• Ignoring delimiters when data is separated by commas or tabs.
• Assuming output is a matrix instead of a cell array.

Always check the file format and specify delimiters if needed.

matlab

fileID = fopen('data.csv','r');
% Wrong: missing delimiter for CSV
% data = textscan(fileID, '%s %d %f');

% Right: specify delimiter
 data = textscan(fileID, '%s %d %f', 'Delimiter', ',');
fclose(fileID);

Quick Reference

Tips for using textscan effectively:

• Use fopen and fclose to manage files.
• Match formatSpec to your data types (e.g., %s for strings, %d for integers, %f for floats).
• Specify delimiters with 'Delimiter' option if data is not space-separated.
• Use 'HeaderLines' to skip unwanted lines.
• Remember output is a cell array; access data with curly braces.

Key Takeaways

Use textscan with a file ID and format string to read mixed data types from text files.

Always open files with fopen and close them with fclose to avoid errors.

Specify delimiters and header lines to match your file's structure.

Output from textscan is a cell array; access each column with curly braces.

Check your format specifiers carefully to match the data types in your file.