Creating a MATLAB App Designer Example

MATLAB App Designer is a tool used to design and build professional apps without needing to be an expert in programming. It is particularly useful for engineers and scientists who want to automate their work or make the results of their code more interactive. This guide provides a comprehensive example of how to use MATLAB App Designer to create a simple yet functional app. We will walk through the steps of building an app that allows users to input a mathematical function and display its plot, providing interactive elements for parameter adjustment.

1: Getting Started with MATLAB App Designer

To begin, open MATLAB and navigate to the "Home" tab. From there, click on "App Designer" under the "File" section. App Designer provides a drag-and-drop environment to design the graphical interface (GUI) of your app. The user interface is divided into two key sections: the design view and the code view. In the design view, you can visually lay out buttons, sliders, labels, and other components. The code view allows you to write the logic that governs the behavior of these components.
After opening App Designer, select "New" and choose "Blank App" to start your new project. You will be presented with a blank canvas where you can design your app layout.

2: Designing the User Interface

The app we are going to create will have a text input field for entering a mathematical function, a button to plot the function, and axes to display the plot. Here's how to add and configure these components:

• Step 1: From the Component Library on the left-hand side, drag a "Numeric Edit Field" onto the canvas. This will be used for the input of the function parameter.
• Step 2: Drag a "Button" component onto the canvas. Set its text label to "Plot Function" by clicking on the button and editing its properties.
• Step 3: Drag an "Axes" component from the library onto the canvas. This will be used to display the graph of the mathematical function.

It's important to position these components logically so the app looks clean and user-friendly. You can also customize the size, fonts, and colors of these components in the Property Inspector.
Once the layout is complete, it should look something like this:

Component	Purpose
Numeric Edit Field	To input the value of the function parameter
Button	To trigger the plotting of the function
Axes	To display the graph of the function

3: Writing the Code for Interactivity

Now that the design is ready, it's time to add the code that makes the app functional. Switch to "Code View" by clicking the button at the top of the App Designer. This is where you can program what happens when the user interacts with the app.
We need to write code that takes the user input from the Numeric Edit Field, plots the function on the axes, and updates the plot when the button is clicked.

Here’s a breakdown of the code needed:

• Step 1: Add a function that executes when the "Plot Function" button is clicked. This function should retrieve the value from the Numeric Edit Field and generate a plot.

matlab
% Callback function for the Plot Button
function PlotButtonPushed(app, event)
    % Get the user input
    userInput = app.NumericEditField.Value;
    
    % Generate X values for the plot
    x = linspace(-10, 10, 100);
    
    % Compute the function values using user input
    y = sin(userInput * x);  % Example function
    
    % Plot the function
    plot(app.UIAxes, x, y);
    
    % Add labels and grid
    xlabel(app.UIAxes, 'X-axis');
    ylabel(app.UIAxes, 'Y-axis');
    grid(app.UIAxes, 'on');
end

The code starts by obtaining the input from the Numeric Edit Field. It then uses this input to scale the sin(x) function (for this example), calculates values for y, and plots them on the axes. You can adjust the function according to the complexity or type of calculation needed. Adding labels and grid lines improves the plot’s readability.

4: Testing and Debugging

Once the design and code are complete, it’s time to test the app. Click the green "Run" button at the top of the App Designer to launch your app. Enter a value in the input field and click "Plot Function" to see the graph. You should be able to interact with the app smoothly. If there are any issues, check the error messages in MATLAB’s command window, or inspect the values and functions in your code.

Debugging tips include:

• Check variable names and types: Ensure that all variable names in your code match those in your design. For example, the Numeric Edit Field should have the correct identifier (like app.NumericEditField).
• Ensure plot compatibility: If your function does not produce valid numerical values for certain inputs, ensure you handle such cases within the code to avoid app crashes.

5: Enhancing the App with More Features

While this app is functional, it’s quite simple. You can add additional features to enhance the app's utility and usability:

• Add multiple input fields: For more complex functions, you might want to allow the user to enter several parameters.
• Interactive sliders: You can use sliders to dynamically adjust the values in the plot.
• Dropdown menus: A dropdown can be added to let users select different functions to plot, such as sine, cosine, or tangent.

Here's an example of adding a slider to adjust the amplitude of the sine wave in real time:

matlab
% Slider callback function
function AmplitudeSliderValueChanged(app, event)
    amplitude = app.AmplitudeSlider.Value;
    x = linspace(-10, 10, 100);
    y = amplitude * sin(x);
    plot(app.UIAxes, x, y);
end

With these additions, your app becomes more interactive and gives users more control over the output. This flexibility is one of the main strengths of MATLAB App Designer.

Conclusion

MATLAB App Designer simplifies the process of creating interactive applications, making it accessible for those who may not have extensive programming experience. The drag-and-drop interface, combined with the ease of integrating MATLAB functions, makes it an ideal tool for creating custom apps for data visualization, analysis, or automation. This tutorial has provided a basic example, but the possibilities for extending functionality are vast. With more practice, you can create highly sophisticated apps tailored to your specific needs.