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How do I extract data from a specific subplot in a MATLAB figure?

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I have a matlab figure with 12 subplots (6X2 figures) and I intend to convert certain subplots into data (whose position I know). I have seen tutorials where MATLAB figures where converted to data but could not find one that handled extraction of data from subplots.
I am new to matlab and am having difficulties figuring out how to do this.
Any help is much appreciated!

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Accepted Answer

Luna
Luna on 27 Nov 2019
Edited: Luna on 27 Nov 2019
Hi,
If you don't have the handles of the plot in the figure here is a demonstration for you.
Please read the comments carefully.
%% demo data preallocation
n = zeros(1,12);
x = cell(12,1);
y = cell(12,1);
hFig = figure;
% randomly creating x and y data and plotting
for i = 1:12
n(i) = randi(20,1,1);
x{i} = rand(n(i),1);
y{i} = rand(n(i),1);
hAxes{i} = subplot(6,2,i); % hAxes axis object handles in a cell array (12 handles you have)
hPlot{i} = plot(hAxes{i},x{i},y{i},'LineStyle','none','Marker','*'); % hPlot plot line object handles (12 handles you have)
end
% -------------------------------------------%
% Gathering data from plotted figure
%% FIRST OPTION IN CASE YOU HAVE HANDLES
%% If you know the position use this: (That I choose the 6th position)
myPlotHandle = hPlot{6};
xdata = myPlotHandle.XData;
ydata = myPlotHandle.YData;
% You can also use this from the position: (Axes' children is a plot line object. Our hPlot{6} is hAxes{6}.Children )
xdata = hAxes{6}.Children.XData;
ydata = hAxes{6}.Children.YData;
%%% OR %%%
%% SECOND OPTION IN CASE YOU DON'T HAVE THE OBJECT HANDLES
% click to a point or a data line in the axis. You should click on a data
% plotted.
% run the code below: (gco function gets you the current object(that means last focused or last clicked object), in this case that will be your plot handle like above)
myPlotHandle = gco;
xdata = obj.XData;
ydata = obj.YData;
% you can click for each 12 plot data and run the code so you will get them
% one by one.

  2 Comments

Harishankar Anil Karingathuruthil
Thank you, I tried with my file and it works.
Thank you very much!
Also FYI I used a different code to get the results from an alreaady existing MATLAB figure.
h=openfig('your_file_name.fig');
handles=findobj(h,'Type','line');
x=get(handles(1),'Xdata');
y=get(handles(1),'Ydata');
Here 1 is taken as the index of the subplot.
Cheers!
Luna
Luna on 2 Dec 2019
Your welcome :) Please accept answer if it works, thanks :)

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More Answers (1)

per isakson
per isakson on 27 Nov 2019
Edited: per isakson on 27 Nov 2019
This illustrates the old way to do it. (There might be shortcut nowadays.)
%% Example from the documentation of subplot
subplot(2,1,1);
x = linspace(0,10);
y1 = sin(x);
plot(x,y1)
%
subplot(2,1,2);
y2 = sin(5*x);
plot(x,y2)
%% Recover x, y1 and y2
ohf = findobj(gcf); % gcf get current figure
%%
oha = findobj( ohf(1), 'Type','axes' ); % find the two axes
%%
oh1 = findobj( oha(1), 'Type','line' ); % find the line of the first axes
%%
all( oh1.XData == x ) % check if the data of the plot is equal to
all( oh1.YData == y2 ) % the data plotted
%%
oh2 = findobj( oha(2), 'Type','line' );
%%
all( oh2.XData == x )
all( oh2.YData == y1 )
Which axes corresponds to which plot? The Position helps to find out
>> oha(1).Position
ans =
0.13 0.11 0.775 0.34116
>> oha(2).Position
ans =
0.13 0.58384 0.775 0.34116
>>
oha(2) is the top one
ADDENDUM
Don't reinvent the wheel before checking with the File Exchange. (as I just did).

  2 Comments

per isakson
per isakson on 27 Nov 2019
ohf = findobj(gcf); % gcf get current figure
%%
oha = findobj( ohf(1), 'Type','axes' );
may be replaced by a better way
oha = findobj( gcf, 'Type','axes' );
The figures can alternatively be found by
>> ohf = findobj( 0, 'Type', 'figure' );
>> ohf
ohf =
Figure (1) with properties:
Number: 1
Name: ''
Color: [0.9400 0.9400 0.9400]
Position: [680 678 560 420]
Units: 'pixels'
With many figures one has to find a way to distinguish between them.
It's more robust not to use gcf, gca, gco in code.
Harishankar Anil Karingathuruthil
Thank you for the codes,
FYI I also found another method too, please check the comment in the above post!

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