MATLAB: Is it possible to create a slider with a logarithmic scale within MATLAB 7.6 (R2008a)

calbackguiguideMATLABslideuicontroluserdata

I would like to create a slider whose value changes on a logarithmic scale, not a linear scale.

Best Answer

The ability to specify a logarithmic scale for a slider is not available in MATLAB 7.6 (R2008a). To implement such a slider, you will need to convert its linear value into a logarithmic value before using it in your GUI.

For example, the following slider has a range of 10^0 to 10^2:

range = [10^0 10^2];
h = uicontrol('style', 'slider', ...
      'position', [50 50 200 20],...
      'min', log10(range(1)),...
      'max', log10(range(2)),...
      'callback', @(src,event)set(src,'UserData',10^get(src,'Value')));

To query the value of the slider, now you would need to query its "UserData" property instead of its "Value" property. For example,

get(h, 'UserData')

This slider has a leftmost value of 1 and a rightmost value of 100. Notice how the center value is 10, not 50.

Related Solutions

MATLAB: Increasing slider value of a GUI

See https://www.mathworks.com/help/matlab/ref/uicontrol-properties.html#property_SliderStep

figure;
uicontrol('Style', 'Slider', 'Position', [10, 10, 200,20], ...
          'SliderStep', [1/29, 0.1], ...
          'Min', 10, 'Max', 300, 'Value', 10, ...
          'Callback', 'disp(get(gcbo, ''Value''))')

The range goes from 10 to 300, which is a distance of 290. To get a stepsize of 10, the SliderStep must be 10/290, or 1/29. You should expect rounding errors, so fix the value in the callback:

uicontrol('Style', 'Slider', 'Position', [10, 10, 200,20], ...
          'SliderStep', [1/29, 0.1], ...
          'Min', 10, 'Max', 300, 'Value', 10, ...
          'Callback', mySliderCB);
function mySliderCB(SliderH, EventData)
Value = round(get(SliderH, 'Value'));
set(SliderH, 'Value', Value);
...

MATLAB: How to Move a Slider- bar when push button presses in GUI

Guide or app designer?

The slider property 'Value' determines the position of the slider bar. The value must be between the slider limits.

To move the slider when the pushbutton is pressed, the pushbutton callback function needs to change the value property of the slider. Add to the current value to move it forward. Subtract from it to move backward.

In guide, the code for the forward button might include something like this (untested)

sVal = get(handles.slider1,'Value');
set(handles.slider1,'Value',sVal+2);

In app designer, it might include this

app.slider1.Value = app.slider1.Value + 2;

Of course you'll want to include a check that only adjusts the value if the result is within the slider limits. You'll also want to set the amount you change Value to meet your needs.

Best Answer

Related Solutions

MATLAB: Increasing slider value of a GUI

MATLAB: How to Move a Slider- bar when push button presses in GUI

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