How do I extract data from MATLAB figures?

Yes, you can extract the data from curves in MATLAB figures (.fig files) even without the original code! Since .fig files store the plotted data internally, MATLAB provides easy ways to access it programmatically. I'll cover two main methods: direct extraction (if you have MATLAB access) and digitization tools (if you only have images of the figures).

 Direct Extraction from .fig Files 

This pulls the exact X and Y data from the curves without any approximation.

1. Open the Figure:

   matlab

    

   openfig('your_figure.fig');  % Replace with your file name

    

    

2. Get the Axes and Line Handles:

   matlab

    

   ax = gca;  % Get current axes
   lines = findobj(ax, 'Type', 'line');  % Find all curve lines

    

    

3. Extract Data:

   matlab

    

   for i = 1:length(lines)
       x_data = get(lines(i), 'XData');  % X values for curve i
       y_data = get(lines(i), 'YData');  % Y values for curve i
       
       % Display or save
       disp(['Curve ' num2str(i) ':']);
       disp([x_data(:), y_data(:)]);  % Shows as [X Y] matrix
       
       % Optionally save to CSV
       writematrix([x_data(:), y_data(:)], ['curve_' num2str(i) '.csv']);
   end

    

    
   • If there are multiple curves, this loops through them.
   • For subplots or other elements (e.g., error bars), use findobj with more filters like 'Tag' if set.
   • No need to display the figure—run this on a closed file too!

   Example output: A matrix of [X Y] pairs you can plot, analyze, or export.