## File: README.md # shiny [](https://CRAN.R-project.org/package=shiny) [](https://github.com/rstudio/shiny/actions) [](https://forum.posit.co/new-topic?category=shiny&tags=shiny) Easily build rich and productive interactive web apps in R — no HTML/CSS/JavaScript required. ## Features * An intuitive and extensible [reactive programming](https://en.wikipedia.org/wiki/Reactive_programming) model which makes it easy to transform existing R code into a "live app" where outputs automatically react to new user input. * Compared to event-based programming, reactivity allows Shiny to do the minimum amount of work when input(s) change, and allows humans to more easily reason about complex [MVC logic](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller). * A prebuilt set of highly sophisticated, customizable, and easy-to-use widgets (e.g., plots, tables, sliders, dropdowns, date pickers, and more). * An attractive default look based on [Bootstrap](https://getbootstrap.com/) which can also be easily customized with the [bslib](https://github.com/rstudio/bslib) package or avoided entirely with more direct R bindings to HTML/CSS/JavaScript. * Seamless integration with [R Markdown](https://shiny.rstudio.com/articles/interactive-docs.html), making it easy to embed numerous applications natively within a larger dynamic document. * Tools for improving and monitoring performance, including native support for [async programming](https://posit.co/blog/shiny-1-1-0), [caching](https://talks.cpsievert.me/20201117), [load testing](https://rstudio.github.io/shinyloadtest/), and more. * [Modules](https://shiny.rstudio.com/articles/modules.html): a framework for reducing code duplication and complexity. * An ability to [bookmark application state](https://shiny.rstudio.com/articles/bookmarking-state.html) and/or [generate code to reproduce output(s)](https://github.com/rstudio/shinymeta). * A rich ecosystem of extension packages for more [custom widgets](http://www.htmlwidgets.org/), [input validation](https://github.com/rstudio/shinyvalidate), [unit testing](https://github.com/rstudio/shinytest), and more. ## Installation To install the stable version from CRAN: ```r install.packages("shiny") ``` ## Getting Started Once installed, load the library and run an example: ```r library(shiny) # Launches an app, with the app's source code included runExample("06_tabsets") # Lists more prepackaged examples runExample() ``` For more examples and inspiration, check out the [Shiny User Gallery](https://shiny.rstudio.com/gallery/). For help with learning fundamental Shiny programming concepts, check out the [Mastering Shiny](https://mastering-shiny.org/) book and the [Shiny Tutorial](https://shiny.rstudio.com/tutorial/). The former is currently more up-to-date with modern Shiny features, whereas the latter takes a deeper, more visual, dive into fundamental concepts. ## Join the conversation If you want to chat about Shiny, meet other developers, or help us decide what to work on next, [join us on Discord](https://discord.com/invite/yMGCamUMnS). ## Getting Help To ask a question about Shiny, please use the [RStudio Community website](https://forum.posit.co/new-topic?category=shiny&tags=shiny). For bug reports, please use the [issue tracker](https://github.com/rstudio/shiny/issues) and also keep in mind that by [writing a good bug report](https://github.com/rstudio/shiny/wiki/Writing-Good-Bug-Reports), you're more likely to get help with your problem. ## Contributing We welcome contributions to the **shiny** package. Please see our [CONTRIBUTING.md](https://github.com/rstudio/shiny/blob/main/.github/CONTRIBUTING.md) file for detailed guidelines of how to contribute. ## License The shiny package as a whole is licensed under the MIT License. See the [LICENSE](LICENSE) file for more details. ## R version support Shiny is supported on the latest release version of R, as well as the previous four minor release versions of R. For example, if the latest release R version is 4.3, then that version is supported, as well as 4.2, 4.1, 4.0, 3.6. --- ## File: inst/examples-shiny/11_timer/Readme.md The function `invalidateLater()` can be used to invalidate an observer or reactive expression in a given number of milliseconds. In this example, the output `currentTime` is updated every second, so it shows the current time on a second basis. --- ## File: inst/examples-shiny/10_download/Readme.md We can add a download button to the UI using `downloadButton()`, and write the content of the file in `downloadHandler()` in the `server` function. --- ## File: inst/examples-shiny/09_upload/Readme.md We can add a file upload input in the UI using the function `fileInput()`, e.g. `fileInput('foo')`. In the `server` function, we can access the uploaded files via `input$foo`. --- ## File: inst/examples-shiny/08_html/Readme.md Normally we use the built-in functions, such as `textInput()`, to generate the HTML UI in the R script `ui.R`. Actually **shiny** also works with a custom HTML page `www/index.html`. See [the tutorial](http://shiny.rstudio.com/tutorial/) for more details. --- ## File: inst/examples-shiny/07_widgets/Readme.md This example demonstrates some additional widgets included in Shiny, such as `helpText` and `actionButton`. The latter is used to delay rendering output until the user explicitly requests it (a construct which also introduces two important server functions, `eventReactive` and `isolate`). --- ## File: inst/examples-shiny/06_tabsets/Readme.md This example demonstrates the `navset_*` and `nav_panel` widgets from the `bslib` package. Notice that outputs that are not visible are not re-evaluated until they become visible. Try this: 1. Scroll to the bottom of the `server` function. You might need to use the *show with app* option so you can easily view the code and interact with the app at the same time. 2. Change the number of observations, and observe that only `output$plot` is evaluated. 3. Click the Summary tab, and observe that `output$summary` is evaluated. 4. Change the number of observations again, and observe that now only `output$summary` is evaluated. --- ## File: inst/examples-shiny/05_sliders/Readme.md This example demonstrates Shiny's versatile `sliderInput` widget. Slider inputs can be used to select single values, to select a continuous range of values, and even to animate over a range. --- ## File: inst/examples-shiny/04_mpg/Readme.md This example demonstrates the following concepts: - **Global variables**: The `mpgData` variable is declared outside of the `ui` and `server` function definitions. This makes it available anywhere inside `app.R`. The code in `app.R` outside of `ui` and `server` function definitions is only run once when the app starts up, so it can't contain user input. - **Reactive expressions**: `formulaText` is a reactive expression. Note how it re-evaluates when the Variable field is changed, but not when the Show Outliers box is unchecked. --- ## File: inst/examples-shiny/03_reactivity/Readme.md This example demonstrates a core feature of Shiny: **reactivity**. In the `server` function, a reactive called `datasetInput` is declared. Notice that the reactive expression depends on the input expression `input$dataset`, and that it's used by two output expressions: `output$summary` and `output$view`. Try changing the dataset (using *Choose a dataset*) while looking at the reactive and then at the outputs; you will see first the reactive and then its dependencies flash. Notice also that the reactive expression doesn't just update whenever anything changes--only the inputs it depends on will trigger an update. Change the "Caption" field and notice how only the `output$caption` expression is re-evaluated; the reactive and its dependents are left alone.