Error in event_data("plotly_hover")? ( r plotly, shiny)

Question

Within a Shiny app, I'm trying to link multiple plots. To do this, I need to be able to retrieve hover data with something like event_data("plotly_hover"). Although this has worked for me before, today for some reason I've been running into a problem I haven't been able to troubleshoot. When I hover over any plotly object and display the hover event data, this error is returned within the Shiny app:

Warning: Error in cat: argument 1 (type 'list') cannot be handled by 'cat'

In the past, using event_data(...) on a plotly object has worked well for me so I'm left scratching my head about what may be going on. Here is some self-contained sample code:

ui <- fluidPage(
  plotlyOutput("singlePlot"),
  verbatimTextOutput("hoverData")
)

server <- function(input, output, session) {
  output$singlePlot <- renderPlotly({
    p <- plot_ly(x = 1:10, y = 1:10, color = I("red"), marker = list(color = "blue"))
    p
  })

  output$hoverData <- renderText(event_data("plotly_hover"))
}


shinyApp(ui = ui, server = server)

In theory I should see something like this:

      curveNumber  pointNumber      x      y 
1               0            1      1      4

But I'm left with the error above. Any ideas on what might be going on?

Mark · Accepted Answer · 2019-03-26 20:03:51Z

0

I think it is because renderText doesn't know how to treat a dataframe, as the name suggests it renders text, nothing else that does not meet the "string" qualification will work probably. Wrapping it in as.character solves your issue too. renderText( as.character(event_data("plotly_hover")))

ui <- fluidPage(
  plotlyOutput("singlePlot"),
  verbatimTextOutput("hoverData")
)

server <- function(input, output, session) {
  output$singlePlot <- renderPlotly({
    p <- plot_ly(x = 1:10, y = 1:10, color = I("red"), marker = list(color = "blue"))
    p
  })

  output$hoverData <- renderText( as.character(event_data("plotly_hover")))
}


shinyApp(ui = ui, server = server)

answered Mar 26, 2019 at 20:03

Mark

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3 Comments

Felix T. Over a year ago

I found out renderPrint() worked well, but I wasn't quite sure why. Thanks for the explanation!

Mark Over a year ago

you're welcome, and renderPrint is the better way to go at it here yes. Enjoy the shiny experience! (I'm guessing you are relatively new to it?)

Felix T. Over a year ago

Exactly-- I'm still getting a hang of it. Thanks!

Felix T. · Accepted Answer · 2019-03-25 16:18:49Z

0

Okay-- I found the solution... kind of silly, but using renderPrint() instead of renderText() works seamlessly. Whoops! Thanks.

answered Mar 25, 2019 at 16:18

Felix T.

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