How can I extract data from a .fig file in MATLAB?

Question

I know this is really basic, but I am new to MATLAB. After opening a .fig file, how do you actually work with the plotted data in the command window? All I see is the plot.

Answer 1

Try hgload and then poke around the graphics handle structure it returns. For example, if you plot and save the following:

x=0:.01:10;
y=sin(x);
h=plot(x,y);
saveas(h,'testfigure.fig');

Clear your workspace, and open the saved figure using hgload:

clear
close all
h=hgload('testfigure.fig');

You can inspect the figure's handle h by calling

get(h)

Or delve further into the axes/titles/legends by calling

ch=get(h,'Children');

If you're using the code in my example, you should only have one child for the figure, which will be the axes. Call the children of the axes, and you should have one line.

l=get(ch,'Children');

Next, call the 'Xdata' and 'Ydata' fields of the line, and you have your original data.

x=get(l,'Xdata');
y=get(l,'Ydata');

If you have a more complicated figure than just axes, it gets a little tougher. You'll need to explore each child to determine if it's the plot you wanted to extract data from.

Answer 2

Actually, you don't even have to display the figure in order to get the data. FIG files are stored in the standard Matlab MAT format, that you can read using the built-in load() function. The figure handles and data are stored in a structure that you can easily understand and process.

Answer 3

Here's a really simple way:

Click on the object that you want to get the data from. There will be no indication that you have clicked on it.

>> xd = get(gco,'XData');
>> yd = get(gco,'YData');

Sometimes it can be hard to click on the line, or other object, itself. If you have this problem, click on the axes that contains the child(ren) you are interested in, then:

>> kids = get(gca,'Children');

This will give you an array of handles to the various children. You can try getting them one at a time by indexing into kids, or use the following to get all data at once. This will return the results as a cell array, which can be a little tricky if you haven't used them before:

>> xd = get(kids,'XData');
>> yd = get(kids,'YData');
>> xd1 = xd{1}; %# X Data from first line

Answer 4

Use the HGLOAD command. Reference available here.