MATLAB: Discretizing matlab slider GUI

discretizationguideslider

Hi all. I'm wondering how to make a slider within Matlab GUI whose values are discretized.
So for example, I want to create a simple slider that cycles through integers 1 – 13.
I have tried adjusting the control properties Max / Min and sliderStep. These work fine for discretizing the slider arrows, but dragging the slider "square" itself and moving it to the left and right is still rather "continuous". I want to only be able to see or select integers within the range. Is this possible?
Thanks, Hamad

Best Answer

Hamad - you will have to add some code in order to discretize the slider for the case where you slide the "slider" without using the arrows. In the yourGuiName_OpeningFcn of a GUI named yourGuiName, I added the following code
 function yourGuiName_OpeningFcn(hObject, eventdata, handles, varargin)
 handles.output = hObject;
 % add a continuous value change listener
 if ~isfield(handles,'hListener')
    handles.hListener = ...
        addlistener(handles.slider1,'ContinuousValueChange',@respondToContSlideCallback);
 end
 % set the slider range and step size
 numSteps = 13;
 set(handles.slider1, 'Min', 1);
 set(handles.slider1, 'Max', numSteps);
 set(handles.slider1, 'Value', 1);
 set(handles.slider1, 'SliderStep', [1/(numSteps-1) , 1/(numSteps-1) ]);
 % save the current/last slider value
 handles.lastSliderVal = get(handles.slider1,'Value');
 % Update handles structure
 guidata(hObject, handles);
I'm not sure if you are using the slider Callback or have created something similar to the above which is more flexible. So all we've done is to create the listener, initialized the slider, and updated the handles structure.
Now we have to define the callback, respondToContSlideCallback as
 % --- Executes on slider movement.
 function respondToContSlideCallback(hObject, eventdata)
 % hObject    handle to slider1 (see GCBO)
 % eventdata  reserved - to be defined in a future version of MATLAB
 % Hints: get(hObject,'Value') returns position of slider
 %        get(hObject,'Min') and get(hObject,'Max') to determine range of slider
 % first we need the handles structure which we can get from hObject
 handles = guidata(hObject);
 % get the slider value and convert it to the nearest integer that is less
 % than this value
 newVal = floor(get(hObject,'Value'));
 % set the slider value to this integer which will be in the set {1,2,3,...,12,13}
 set(hObject,'Value',newVal);
 % now only do something in response to the slider movement if the 
 % new value is different from the last slider value
 if newVal ~= handles.lastSliderVal
     % it is different, so we have moved up or down from the previous integer
     % save the new value
     handles.lastSliderVal = newVal;
     guidata(hObject,handles);
    % display the current value of the slider
    disp(['at slider value ' num2str(get(hObject,'Value'))]);
 end
Now when you run the code, you will only see the integer values being written to the Command Window whenever you use the slider arrow buttons or manually move the slider. The difference between each integer will always be one. So we ignore any "slides" in between any two consecutive integers.
Try the above and see what happens!
Related Question