uiknob

Create a continuous knob in a figure.

fig = uifigure;
kb = uiknob(fig);

Determine the knob limits.

limits = kb.Limits

limits =

     0   100

Change the limits and the knob value.

kb.Limits = [-10 10];
kb.Value = 5;

Create a discrete knob.

fig = uifigure;
kb = uiknob(fig,'discrete');

Change the knob states. Associate specific data with the knob states by configuring ItemsData. In this case, ItemsData reflects temperatures in degrees Fahrenheit.

kb.Items = {'Cold', 'Warm', 'Hot'};
kb.ItemsData = {32, 80, 212};

Get the temperature associated with the current knob value.

degrees = kb.Value

degrees =

    32

Copy and paste the following code into a file named displayknobvalue.m on your MATLAB path. This code creates a window containing a discrete knob and an edit field. It specifies a ValueChangedFcn callback to update the edit field when the knob is turned.

function displayKnobValue
% Create figure window

fig = uifigure('Position',[100 100 283 275]);

% Create the text field
txt = uieditfield(fig,'text',...
    'Position', [69 82 100 22]);

% Create the knob
kb = uiknob(fig,'discrete',...
    'Position',[89 142 60 60],...
    'ValueChangedFcn',@(kb,event) knobTurned(kb,txt));
end

% Code the knob callback function
function knobTurned(knob,txt)
txt.Value = knob.Value;
end

Run displayKnobValue, and then turn the knob. When you release the mouse button, the edit field is updated to reflect the new knob value.

Copy and paste the following code into a file named showknobvalue.m on your MATLAB path. This code creates a window containing a continuous knob and a label field. It specifies a ValueChangedFcn callback to update the label when the knob is turned.

function showKnobValue
% Create figure window and components
fig = uifigure('Position',[100 100 283 275]);

% Create label
lbl = uilabel(fig,...
    'Position',[218 177 50 15],...
    'Text','0');

% Create knob
kb = uiknob(fig,...
    'Position',[89 142 60 60],...
    'ValueChangedFcn', @(kb,event) knobTurned(kb,lbl));
end

% Create ValueChangedFcn callback
function knobTurned(kb,lbl)
num = kb.Value;
lbl.Text = num2str(num);
end

Run showKnobValue and turn the knob. When you release the mouse button, the label is updated to reflect the new knob value.

Copy and paste the following code into a file named showchangingvalue.m on your MATLAB path. This code creates a window containing a continuous knob and an edit field. It specifies a ValueChangingFcn callback to keep updating the edit field as the knob is being turned.

function showChangingValue
% Create figure window
fig = uifigure('Position',[100 100 283 275]);

% Create numeric edit field
num = uieditfield(fig,'numeric',...
    'Position',[69 82 100 20]);

% Create knob
kb = uiknob(fig,...
    'Position',[89 142 60 60],...
    'ValueChangingFcn',@(kb,event) knobTurned(kb,event,num));
end

% Create ValueChangingFcn callback
function knobTurned(kb,event,num)
num.Value = event.Value;
end

Run showChangingValue, and turn the knob. As you do so, the edit field is updated to show the changing knob values.

Copy and paste the following code into a file named increaseOnly.m on your MATLAB path. This code creates a window containing a continuous knob. It specifies a ValueChangedFcn callback for the knob to display an Invalid Value dialog box when the app user attempts to decrease the knob value.

function increaseOnly
% Create figure window
fig = uifigure('Position',[100 100 400 275]);

% Create knob
kb = uiknob(fig,...
    'Position',[150 125 60 60],...
    'ValueChangedFcn',@(kb,event) nValChanged(kb,event,fig));
end

% Create ValueChangedFcn callback
function nValChanged(kb,event,fig)
newvalue = event.Value;
previousvalue = event.PreviousValue;
if previousvalue >  newvalue
   uialert(fig, 'Increase value only. Value reverted to previous value.', ...
        'Invalid Value');
   kb.Value = previousvalue;
end
end

Run increaseOnly, increase the knob value, and then try to decrease it. When you try to decrease the value, an error dialog box displays and the value is reverted to the previous valid value. You can only increase the knob value.