Sharing and Embedding Trelliscope

Sharing Trelliscope displays

Trelliscope displays are best used as a way to explore data with colleagues, particularly domain experts who can provide insight into what is being seen. As such, it is important to be able to share Trelliscope displays with others. There are a few ways to do this.

Trelliscope displays are self-contained serverless web applications that can be easily shared with others. They are designed to be able to be used completely offline (no web dependencies for libraries, fonts, etc.), so you can share them with others without having to worry about hosting them on a server with complex dependencies. The only requirement is that the person you are sharing with has a modern web browser.

Embedding Trelliscope in R Markdown

We have worked to make it easy to embed Trelliscope displays in R Markdown documents. It is as easy as calling view_trelliscope() on a Trelliscope data frame. However, there are a few things to keep in mind.

First, you can only embed Trelliscope outputs in HTML-formatted output types that aren’t self-contained. We have tested the following output formats:

• rmarkdown::html_vignette
• rmarkdown::html_document
• rmarkdown::slidy_presentation
• revealjs::revealjs_presentation

Second, your output chunk needs to have a name. This will be used to determine where to write the output of the display.

Third, you need to leave the path option of as_trelliscope_df() blank. Trelliscope will automatically determine the path to use, which will be a relative path inside your R Markdown output directory.

Additionally, you might consider setting some chunk options to make the output look better. For example, it is a good idea to set out.width="100%" and hard-code the height (out.height="___px") to control the size of the display. We have also added support for a scale chunk option that can be used to scale the output UI so that it doesn’t appear so large when rendered in confined spaces.

Below is an example of a chunk that will embed a Trelliscope display in an R Markdown document with these considerations in mind.

---
title: "Trelliscope RMarkdown Embedding"
output:
  html_document:
    self_contained: false
---

# Mars Rover Images

```{r mars_trelliscope, out.width="100%", out.height="700px", scale=0.5}
library(trelliscope)
d <- as_trelliscope_df(mars_rover, name = "mars rover")
view_trelliscope(d)
```

Another option for embedding Trelliscope displays in R Markdown documents is to pre-render them and host them somewhere on the internet and then stick an iframe tag in your R Markdown document.

Embedding Trelliscope in Quarto

Similar to R Markdown, when embedding in Quarto, you can set necessary output options in your code block to help a display render in the way you would like. For example:

```{r}
#| label: mars_trelliscope
#| out-width: "100%"
#| out-height: "500px"
#| scale: 0.5
#| output: asis
library(trellicope)
d <- as_trelliscope_df(mars_rover, name = "mars rover")
view_trelliscope(d)
```

Embedding Trelliscope in Shiny

Trelliscope is a great alternative to Shiny for a wide range of interactive visualization applications. In any situation where you are considering building a Shiny app that provides the user with many controls that produce a visual output, you should consider using Trelliscope instead by producing a data frame of visualizations corresponding to every combination of user input values. Trelliscope displays are easier to build, maintain, and share than shiny apps, and provide the benefit of being able to view many outputs simultaneously, as well as exploring the input parameter space interactively.

It can be the case, however, that you might want to build a Shiny app that allows a user to provide inputs for building a Trelliscope display, or in which you would like a user to be able to view a Trelliscope display. If the latter (no dynamic inputs required for creating the display), we advise to simply build the display up-front and embed it in an iframe somewhere in the Shiny app. For building and displaying dynamically-generated Trelliscope displays, we provide an example below.

In this example, we create a simple app that allows a user to choose a dataset (either mars_rover or none), provide a description for the Trelliscope display, and then view the resulting display.

library(trelliscope)
library(shiny)

tr_dir <- tempfile()
dir.create(tr_dir)
add_trelliscope_resource_path("trelliscope", tr_dir)

ui <- fluidPage(
  titlePanel("Trelliscope Embed in Shiny"),
  sidebarLayout(
    sidebarPanel(
      selectInput(
        "dataset",
        "Choose a dataset:",
        choices = c("mars_rover", "[no data]")),
      textInput("description", "Description:", "[display description]")
    ),
    mainPanel(
      trelliscopeOutput("trelliscope", style = "height: 800px")
    )
  )
)

server <- function(input, output) {
  output$trelliscope <- renderTrelliscope({
    if (input$dataset == "mars_rover") {
      d <- as_trelliscope_df(mars_rover,
        name = "mars rover",
        description = input$description,
        path = file.path(tr_dir, "test"),
        jsonp = FALSE
      )
      d
    } else {
      NULL
    }
  })
}

shinyApp(ui = ui, server = server)

For those with experience in Shiny, most of the above should be straightforward. One main function to call out is add_trelliscope_resource_path(), which allows you to specify a path that the app can look in to find your Trelliscope displays. In the UI, you can use trelliscopeOutput() to specify where a Trelliscope display will be rendered. In the server, you use renderTrelliscope() to write create the display. You must place the display in the path you used with add_trelliscope_resource_path(). The object returned by renderTrelliscope() should be a Trelliscope data frame. Trelliscope will take care of writing the display to the specified path and rendering it in the UI.

Note that when we create our Trelliscope data frame in renderTrelliscope(), we use jsonp = FALSE. If you are using Shiny locally, you can likely stick with the default of jsonp = TRUE. However, if you are deploying your Shiny app to a server, we have noticed that services like shinyapps.io and Posit Connect do not like the data files written out by Trelliscope to be stored as jsonp so you will need to set jsonp = FALSE.