In rstudio/pins: Pin, Discover, and Share Resources

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  eval = requireNamespace("xml2", quietly = TRUE)
)

This vignette demonstrates how you might use pins and Posit Connect together to automate ETL for a Shiny app. Pulling expensive data manipulation out of your Shiny app is a great way to improve performance, and pins makes it easy to schedule data updates in a way that automatically flows into your app.

library(pins)

Sharing tidied data

Imagine you're interested in what's going on in the news, so you've written a little code to scrape the BBC world news feed and turn it into a tidy dataset:

library(xml2)

if (interactive()) {
  xml <- read_xml("http://feeds.bbci.co.uk/news/rss.xml")  
} else {
  # Read a saved version of the data to keep this vignette reproducible
  xml <- read_xml("bbc-news.xml")  
}

items <- xml %>% xml_find_all("//item")

bbc_news <- tibble::tibble(
  title = items %>% xml_find_first("./title") %>% xml_text(),
  date = items %>% xml_find_first("./pubDate") %>% xml_text(),
  url = items %>% xml_find_first("./guid") %>% xml_text()
)
bbc_news

Wouldn't it be nice to spare your colleagues the work of reproducing this data, and provide them directly with the tidy tibble? That's easy to do with pins:

board <- board_connect()
board %>% pin_write(bbc_news)

If you open the pin on RSC (e.g. by running board %>% pin_browse("news_total")), you'll see some metadata about the pin, a preview of the data, and a control panel which allows you to control who can see the data. Assuming you've given your colleagues access, they can now easily pull down the data for their own analysis:

board <- board_connect()
board %>% pin_read("your_name/bbc_news")

Automating

Here the underlying data will be changing regularly, but the pinned data will only change when you run pin_write(). Wouldn't it be great if we could automate that process? One way to do so is with RSC's scheduled reports.

First, take your code and put it in an Rmd:

cat(readLines("connect-automate.txt"), sep = "\n")

Then publish it to Posit Connect, and schedule it to run as often as you like. Assuming that you have Posit Connect 1.9.0 or later you don't need to provide any arguments to board_connect(); pins will automatically publish to the same Connect instance that's running the report.

Shiny apps

If you're using automatically updated data in a Shiny app, you can use pin_reactive_read() to create a reactive dependency so that your app will automatically update shortly after the data changes:

library(shiny)
library(pins)

board <- board_connect()

ui <- fluidPage(
  titlePanel("News from the BBC"),
  htmlOutput("news")
)

server <- function(input, output, session) {
  news <- board %>% pin_reactive_read("hadley/bbc_news")

  output$news <- renderUI({
    title <- htmltools::htmlEscape(news()$title)
    links <- paste0("<a href='", news()$url, "'>", title, "</a>")
    bullets <- paste0("  <li>", links, "</li>", collapse = "\n")
    HTML(paste0("<ul>", bullets, "</ul>"))
  })
}

shinyApp(ui, server)