How to Import .dat Files in MATLAB
A .dat file can be plain text (delimited numbers or tables) or binary data. Choose the method below that matches your file structure.
Method 1: Plain Numeric Text (Recommended)
For files containing space, tab, or comma-separated numbers, use readmatrix().
% Import pure numeric data into an array
data = readmatrix('measurement.dat');
% If the file contains header lines to skip (e.g., skip 2 lines)
data = readmatrix('measurement.dat', 'NumHeaderLines', 2);
% Extract columns
time = data(:, 1);
voltage = data(:, 2);
Method 2: Text .dat with Column Headers (Table Format)
If the file contains text headers at the top of each column, use readtable().
% Import as a table preserving column headers
opts = detectImportOptions('sensor_log.dat', 'FileType', 'text');
T = readtable('sensor_log.dat', opts);
% View first few rows
head(T)
% Access columns by name
x = T.Time;
y = T.Pressure;
Method 3: Quick Load for Space-Delimited Numbers
If the .dat file contains only numbers and no text headers, the built-in load() command imports it directly as a matrix named after the file.
% Loads data into a variable named 'signal_data'
load('signal_data.dat');
% Or assign directly to a variable
A = load('signal_data.dat');
Method 4: Custom Delimiters or Mixed Columns (readmatrix / textscan)
When the file uses specific characters like semicolons, tabs, or spaces as delimiters:
% Specify delimiter explicitly (tab, space, or comma)
data = readmatrix('data.dat', 'Delimiter', '\t', 'NumHeaderLines', 1);
% Alternative using low-level textscan for complex formatting
fileID = fopen('custom.dat', 'r');
C = textscan(fileID, '%f %f %s', 'HeaderLines', 1);
fclose(fileID);
col1 = C{1};
col2 = C{2};
col3_text = C{3};
Method 5: Binary .dat Files (fread)
If the .dat file is in binary format (not readable in a text editor), read it using fopen and fread with the matching data precision:
% Open binary file for reading
fileID = fopen('binary_data.dat', 'rb');
% Read all values as 32-bit floats (single) or 64-bit (double)
raw_data = fread(fileID, [100, Inf], 'double');
% Always close the file handle
fclose(fileID);
Selection Guide:
- Pure numbers: Use
readmatrix('file.dat'). - Numbers with headers: Use
readtable('file.dat'). - Binary file: Use
fopen+fread. - Interactive import: Run
uiimport('file.dat')to preview and select columns visually.
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