MATLAB GUI Examples: Building Applications with App Designer

Introduction
MATLAB's App Designer is a powerful tool that allows users to create professional-quality graphical user interfaces (GUIs) with ease. Whether you're looking to build complex engineering applications, data analysis tools, or simple user input forms, App Designer provides a rich environment with interactive components, a robust programming language, and seamless integration with the rest of the MATLAB environment.

What is App Designer?
App Designer is a drag-and-drop environment in MATLAB that enables users to design interactive applications without needing to be experts in user interface design or programming. It combines the ease of a graphical editor with the power of MATLAB scripting, making it an ideal choice for engineers, scientists, and educators.

App Designer offers a variety of components like buttons, sliders, drop-down menus, and plots, which can be easily configured and linked to MATLAB code. This allows for the rapid development of applications that can run on desktops or be shared as standalone applications.

Getting Started with App Designer
To get started with App Designer, open MATLAB and go to the Home tab. Click on "New" and select "App" from the drop-down menu. This will open the App Designer interface, where you can begin designing your GUI.

The App Designer interface is divided into two main sections: the Design View and the Code View. The Design View is where you create the layout of your app by dragging and dropping components. The Code View is where you write the MATLAB code that controls the behavior of your app.

Example 1: Creating a Simple Calculator App
Let’s walk through the process of creating a simple calculator app in App Designer. This app will allow users to perform basic arithmetic operations like addition, subtraction, multiplication, and division.

1. Design the User Interface

   • Open App Designer and start a new app.
   • Drag and drop four Button components for the operations (+, -, *, /).
   • Add two Edit Field (Numeric) components for input numbers.
   • Add one Edit Field (Numeric) for the result display.
   • Arrange these components logically on the canvas.

2. Write the Code

   • Switch to the Code View by clicking on the "Code View" button.
   • MATLAB automatically generates a template with function callbacks for each button.
   • Implement the functionality for each arithmetic operation in the corresponding button’s callback function.

Example code snippet:

matlab
% Button pushed function: Addition
function AddButtonPushed(app, event)
    app.ResultEditField.Value = app.Number1EditField.Value + app.Number2EditField.Value;
end

% Button pushed function: Subtraction
function SubtractButtonPushed(app, event)
    app.ResultEditField.Value = app.Number1EditField.Value - app.Number2EditField.Value;
end

After coding the functionality, you can run the app directly from App Designer and interact with it as if it were a standalone application.

Example 2: Data Visualization App
Another powerful use of App Designer is in creating data visualization tools. Let’s create an app that plots a sine wave and allows users to modify the frequency and amplitude.

1. Design the User Interface

   • Drag and drop an Axes component for the plot.
   • Add Slider components for adjusting the frequency and amplitude.
   • Add Label components to indicate the purpose of each slider.

2. Write the Code

   • In the Code View, write the callback functions for the sliders to update the plot dynamically based on user input.

Example code snippet:

matlab
% Value changed function: FrequencySlider
function FrequencySliderValueChanged(app, event)
    frequency = app.FrequencySlider.Value;
    amplitude = app.AmplitudeSlider.Value;
    x = linspace(0, 2*pi, 1000);
    y = amplitude * sin(frequency * x);
    plot(app.UIAxes, x, y);
end

This example demonstrates how easy it is to create interactive applications for data analysis and visualization using App Designer.

Advanced Features of App Designer

• Component Library: App Designer comes with a comprehensive library of UI components, including more advanced options like tabs, tables, and tree controls.
• Property Inspector: The Property Inspector allows you to modify the properties of UI components without writing code, such as setting the color, font, or initial values.
• Custom Components: Users can create custom components by combining existing ones or by integrating external libraries.
• Testing and Debugging: App Designer integrates with MATLAB’s debugging tools, allowing you to step through your code, set breakpoints, and inspect variables during app execution.
• Deploying Apps: Once your app is complete, you can package it as a standalone application, a MATLAB app file, or even a web app using MATLAB Compiler.

Best Practices for App Design

• User Experience (UX): Keep the end-user in mind when designing your app. Ensure the layout is intuitive, and components are clearly labeled.
• Modularity: Organize your code into functions and callbacks to keep it manageable and readable.
• Error Handling: Implement error handling to manage unexpected inputs or situations gracefully.
• Performance Optimization: Use efficient coding practices to ensure your app runs smoothly, especially for complex applications or large datasets.

Conclusion
MATLAB's App Designer is a versatile tool that opens up a world of possibilities for creating custom applications. Whether you’re a novice or an experienced MATLAB user, the drag-and-drop interface combined with MATLAB’s robust coding environment allows you to build professional-grade apps with ease. From simple calculators to complex data analysis tools, App Designer can handle it all, making it an invaluable tool in your MATLAB toolkit.

Start experimenting with App Designer today and see how you can enhance your MATLAB experience with custom applications that cater to your specific needs.