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Not an issue - Need some guidance

Hi Kent,

I was trying to create crosshairs on a ggplot2 and this is the best I could come up with. Do you think we can achieve this using native R functions or do we have to resort of Javascript. Given your expertise in this field, was wondering if you could provide your views.

library(shiny)
library(ggplot2)
library(Cairo)   # For nicer ggplot2 output when deployed on Linux

# We'll use a subset of the mtcars data set, with fewer columns
# so that it prints nicely
mtcars2 <- mtcars[, c("mpg", "cyl", "disp", "hp", "wt", "am", "gear")]


ui <- fluidPage(
  fluidRow(
    column(width = 4,
           plotOutput("plot1", height = 300,
                      # Equivalent to: click = clickOpts(id = "plot_click")
                      hover = hoverOpts(id = "plot_hover", delayType = "throttle"),
           )
    )
  ),
  fluidRow(
    column(width = 6,
           h4("Hover Points"),
           verbatimTextOutput("hover_info")
    )
  )
)

server <- function(input, output) {
  output$plot1 <- renderPlot({
    ggplot(mtcars2, aes(wt, mpg)) + 
    geom_point()  + 
    geom_vline(xintercept = xdata(),colour="black", linetype = "longdash") +
    geom_hline(yintercept = ydata(),colour="black", linetype = "longdash") +
    scale_x_continuous(limit = c(0, 5)) +
    scale_y_continuous(limit = c(0, 35))  
  })


  xdata<-reactive({
    ifelse(!is.null(input$plot_hover$x), return(input$plot_hover$x), return(0))
  })

  ydata<-reactive({
    ifelse(!is.null(input$plot_hover$y), return(input$plot_hover$y), return(0))
  })


  output$hover_info <- renderPrint({
    input$plot_hover$x
  }) 
}

shinyApp(ui, server)

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