R Shiny Plot Click with geom bar and facets

Question

I would like to create an interactive plot with shiny and ggplot2 . I have been able to do this successfully with geom_point and other geoms with an obvious x and y axis. When using something like a geom_bar , though, this is harder since you don't have a y variable.

There is a solution here and here to extract the x variable from the click event to do the filtering desired but neither of these handle plots with facets. I would like to use the click option on a ggplot with facets. I tried to adapt the code at the first link, but this hasn't been successful.

library(ggplot2)
library(shiny)

ui <- fluidPage(
  fluidRow(
    plotOutput("plot1", height = 300, width = 300,
               click = "plot1_click",
    )
  ),
  verbatimTextOutput("x_value"),
  verbatimTextOutput("selected_rows")
)

server <- function(input, output) {
  output$plot1 <- renderPlot({
    ggplot(ToothGrowth, aes(supp)) + geom_bar(stat = "count") + facet_wrap(~dose)
  })

  # Print the name of the x value
  output$x_value <- renderPrint({
    if (is.null(input$plot1_click$x)) return()

    lvls <- levels(ToothGrowth$supp)
    lvls[round(input$plot1_click$x)]
  })

  # Print the rows of the data frame which match the x value
  output$selected_rows <- renderPrint({
    if (is.null(input$plot1_click$x)) return()

    keeprows <- round(input$plot1_click$x) == as.numeric(ToothGrowth$supp)
    ToothGrowth[keeprows, ]
  })
}

shinyApp(ui, server)

A click on any of the bars does well to filter to the x values but includes results from all facets. I would like to only include results from the clicked facet.

I have tried using nearPoints with pannelvar1 but it throws an error since I don't have a y variable to pass to it.

Any thoughts?

Answer 1

I changed your last function and got the result I think you want.

  output$selected_rows <- renderPrint({
    if (is.null(input$plot1_click$x)) return()
    panel = input$plot1_click$panelvar1

    keeprows <- round(input$plot1_click$x) == as.numeric(ToothGrowth$supp) & ToothGrowth$dose==panel
    ToothGrowth[keeprows, ]
  })

I am not sure what error you were getting from trying to access panelvar1, but I used the configuration option options(shiny.trace=TRUE) to check out how to access the panel variable (log message added below). Perhaps you were just trying to pull the value from the wrong position

RECV {"method":"update","data":{"plot1_click":{"x":1.1651034873830555,"y":4.268063179119527,"panelvar1":2,"mapping":{"x":"supp","y":null,"panelvar1":"dose"},"domain":{"left":0.4,"right":2.6,"bottom":-0.5,"top":10.5},"range":{"left":213.995433789954,"right":294.520547945205,"bottom":268.013698630137,"top":23.4383561643836},"log":{"x":null,"y":null},".nonce":0.39996409229934216}}}