WebR/Shinylive Overview

George Stagg

R in the browser: webR

The webR logo

The webR project is a version of the R interpreter built for WebAssembly.

Execute R code directly in a web browser, without a supporting R server. Alternatively, run an R process server-side using Node.js

How it works: WebAssembly (2017)

A portable binary code format
Enables high-performance applications on web pages
Near-native execution speed
Supported by most modern browsers

Containerisation
Sandboxing
Interactivity

Reproducibility
Software portability
Universal binaries

R Consortium Submission Working Group

🔗 https://rconsortium.github.io/submissions-wg/

Create clinical trial submission deliverables with open-source software
Consists of Industry and Regulatory members
Pilot 3: Successful Shiny app submission to FDA reviewers

Screenshot of the pilot shiny app submission using webR

Now investigating containers and WebAssembly for Shiny app submission.

🔗 Testing Containers and WebAssembly in Submissions to the FDA - pharmaverse.github.io

🔗 Shiny Based Clinical Submissions - Eric Nantz posit::conf(2024)

Hosting a Shiny app

A workstation, under a desk, running Shiny.
Shiny Server
shinyapps.io/Posit Connect Cloud
Posit Connect enterprise deployment
AWS/Google/Azure cloud hosting

Traditional Shiny App

Bundle and distribute app source?

Transfer source and data to some other machine.
Run the app with a local Shiny server.

Requires a reproducible workflow and software installation:

R/Python interpreter, of the correct version.
Software and environment control: Docker, rix, renv, venv, etc.
Software development tools: RStudio, VSCode, Positron.
Knowledge and experience: Shiny runApp(), debugging.

Shinylive 🔗 https://shinylive.io/r/

Shinylive App

Convert a Shiny app to Shinylive

Install the Shinylive R package:

install.packages("shinylive")

Convert the app:

shinylive::export("myapp", "site")

Binary bundle ready to transfer to another machine or host on a static web service.

Run the application:

httpuv::runStaticServer("site")

or…

python -m http.server
npx http-server

Shinylive in Quarto

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```{shinylive-r}
#| standalone: true
library(shiny)

# Create Shiny UI
ui <- [...]

# Create Shiny server function
server <- function(input, output, session) {
  [...]
}

# Build Shiny app
shinyApp(ui = ui, server = server)
```

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#| standalone: true
#| viewerHeight: 700

library(shiny)
library(bslib)

theme <- bs_theme(font_scale = 1.5)

# Define UI for app that draws a histogram ----
ui <- page_sidebar(theme = theme,
  sidebar = sidebar(open = "open",
    numericInput("n", "Sample count", 50),
    checkboxInput("pause", "Pause", FALSE),
  ),
  plotOutput("plot", width=1100)
)

server <- function(input, output, session) {
  data <- reactive({
    input$resample
    if (!isTRUE(input$pause)) {
      invalidateLater(1000)
    }
    rnorm(input$n)
  })
  
  output$plot <- renderPlot({
    hist(data(),
      breaks = 30,
      xlim = c(-2, 2),
      ylim = c(0, 1),
      xlab = "value",
      freq = FALSE,
      main = ""
    )
    
    x <- seq(from = -2, to = 2, length.out = 500)
    y <- dnorm(x)
    lines(x, y, lwd=1.5)
    
    lwd <- 5
    abline(v=0, col="red", lwd=lwd, lty=2)
    abline(v=mean(data()), col="blue", lwd=lwd, lty=1)

    legend(legend = c("Normal", "Mean", "Sample mean"),
      col = c("black", "red", "blue"),
      lty = c(1, 2, 1),
      lwd = c(1, lwd, lwd),
      x = 1,
      y = 0.9
    )
  }, res=140)
}

# Create Shiny app ----
shinyApp(ui = ui, server = server)

WebAssembly R packages

Binary R packages for WebAssembly are available from CRAN-like repositories

Over 65% of CRAN packages available for webR
🔗 https://repo.r-wasm.org
R-Universe provides bioconductor, custom R packages
🔗 https://r-universe.dev

Recent improvements:
- Improved bundling
- No external dependencies, long-term reproducibility

rwasm package hex logo

Future work and current issues

Not all R packages work under WebAssembly.
Requires a web server, even for local applications.

There will always be good reasons to use a traditional Shiny deployment.
Browser security restrictions: limited networking & database access, no raw socket access.

There are no secrets with a Shinylive app! Anything in the app source can be viewed.