MATLAB: Create a plot with a drop down menu in an App

app designerdrop downMATLABmatlab guiplot

Hello everybody,
i have the following problem and i dont know how to solve it:
I have created an app in Matlab and in this app i select a set of data, which i ll load into the workspace. Next i have 2 drop down menus. With these drop downs i want to select the x-axis and y axis of the workspace.
% Select the set off data and load the workspace variables in the drop down menu
% Button pushed function: ffnenButton
        function ffnenButtonPushed(app, event)
            [name,path] = uigetfile('*.dat', 'Bitte gewünschte dat-Datei auswählen');
            if name==0 return, end
            
            mdfimport(name);
            
                  vars = evalin('base', 'whos');
                  cell_array = cell(size(vars));
                  for i=1:length(vars)
                    cell_array{i} = vars(i).name;
                  end
                  app.dd_achse_x.Items = cell_array;
                  app.dd_achse_y.Items = cell_array;
        end
        
        % x Axis
        % Value changed function: dd_achse_x
        function dd_achse_xValueChanged(app, event)
            xAchse = app.dd_achse_x.Value;
            
        end
        % y Axis
        % Value changed function: dd_achse_y
        function dd_achse_yValueChanged(app, event)
            yAchse = app.dd_achse_y.Value;
            
        end
        % Create Graph
        % Button pushed function: GrapherstellenButton
        function GrapherstellenButtonPushed(app, event)
            plot(xAchse,yAchse,'k-')
        end
As seen above, i want to create a plot with the selected data. This plot should pop up in another figure with fig = uifigure … etc.
But the problem is, that "xAchse" and "yAchse" are not defined in the function.
I hope that someone can help me. If you have any questions, just let me know.
Thanks

Best Answer

I think you don't even need to define callback functions for your dropdowns. They are already properties of your app object.
Basically you can do this: 
function GrapherstellenButtonPushed(app, event)
    plot(app.dd_achse_x.Value,app.dd_achse_y.Value,'k-')
end
There might be a problem. You should check app.dd_achse_y.Value is value of a dropdown item, it might be string or cell array of character vectors. So you might need to convert it to numerical value before you plot.
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