How to store values in cell array?

I made a GUI that allows the user to determine regions in an image by using ROI object. the ROI object return its position as a matrix. I want to save the positions in a cell array when ever the user determine region in the image.

How can I do that?

Answer 1

[madhan ravi]

An example:

A = {rand(4)} %stores the matrix as a cell array if you use curly braces

you can access the elements like a normal one

A{1}(1,1) %first element is obtained

[sara sar]

Thanks so much! it works but the result appears only in command window. It did not change in the workspace:

Also, I want to add more than one element, I mean if the user click the button to determine the region, then I want it to add the value Automatically to the cell array.

[madhan ravi]

Use the option mat2cell(rand(4))

[Stephen23]

"... it works but the result appears only in command window. It did not change in the workspace"

There is no such thing as the workspace: there is the base workspace and all functions (e.g. GUI's and callbacks) have their own independent workspaces:

https://www.mathworks.com/help/matlab/matlab_prog/base-and-function-workspaces.html

If you want to return those values from a GUI to the base workspace then I recommend that you use waitfor and simply return the values when the figure is closed:

function [A,B,C] = myGUI(...)
...
A=[];B=[];C=[];
fgh = figure(...)
... Set A, B, C using nested callback functions
waitfor(fgh)
end

And then simply call it like any other function:

[X,Y,Z] = myGUI(...)

[madhan ravi]

Thank you @stephen

[sara sar]

In fact I'm beginner with using matlab.. could you please explain where should I write what you wrote?

I have this function who is already initialized when I created the GUI:

 % --- Outputs from this function are returned to the command line.
function varargout = untitled_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)% Get default command line output from handles structure
varargout{1} = handles.output;

Then I created a button that allow the user to specify region using ROI object:

% --- Executes on button press in rect.
function rect_Callback(hObject, eventdata, handles)
% hObject    handle to rect (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
  % determine the positions
  h = imrect;
  position = getPosition(h);
  SafeAreas = {position}

I do not understand where should I make the changes that suggested by you @stephen

Thank you so much!

[Stephen23]

@sara sar: if you want to pass data between callback function then use guidata (if you are unfortunately using GUIDE) or use nested functions (if you are happily writing your own GUI):

https://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html

Note that callback functions do not return any output arguments, so there is no point in defining varargout.

If you want to return data from the GUI to the base workspace then either follow what I explained in my last comment, or if you are using GUIDE then use the OutputFcn:

https://www.mathworks.com/help/matlab/creating_guis/initializing-a-guide-gui.html#f10-999738

https://blogs.mathworks.com/videos/2010/02/12/advanced-getting-an-output-from-a-guide-gui/

Note that you can use waitfor inside the OutputFcn.

Answer 2

[Image Analyst]

You don't need a cell array. See attached demo.

The best way to save the coordinates of a segmented image is as a binary image, or as boundaries (after using bwboundaries()).

You can use imwrite() to save the binary image in a .PNG disk file, or use save() to save the boundaries in a .mat file on disk if you need to.

[sara sar]

Thanks, but actually I need to store the positions because I will make some calculation with them.

[Image Analyst]

OK, but not in a cell array. What would you put in the cell(s)? The binary image? The coordinates? Since you'd already have the variables to put into the cell (like you think you'd want), then why use an additional variable of a cell array? Just use the variables themselves and skip the cell array.

[sara sar]

I want to put the coordinates in the cells. The user can specify more than one region using ROI objects. for example: there are 3 cars in the image. the user want to specify 2 of them, then the system will calculate the distance between the cars -that specified by the user- . So, I want to allow the user to specify many regions in the image, then I will store the coordinates of the ROI objects in cell array, after that the system will calculate the distance between them.

[Image Analyst]

See my attached spatial calibration demo.