Hi,
you can use the functions getappdata and setappdata.
let say that in your callback you get the matrix MyData.
% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
X= uigetfile('.txt');
%... some calculation
MyData = rand(4,4);
% In the same callback you open the 2nd GUI
B;
% store MyData in B
Bhandle = findall(0,'Name','B'); % assuming this GUI is really named B.
setappdata(Bhandle ,'MyData',MyData);
Then later, in the callback of GUI B, you can retrieve this data by simply doing :
Bhandle = findall(0,'Name','B');
MyData = getappdata(Bhandle ,'MyData');
