Display the count of clicks in a plot using shiny

Question

I want to build a shiny app that counts the number of clicks I make on any image, but I don't know how to make the counter increase, it just plots the number 1

I tried to create loops inside renderPlot but it doesn't work.

It is necessary to change the path of the files to a directory that contains .jpg images

library(shiny)

ui <- fluidPage(

  titlePanel("Click Count"),

  sidebarPanel(selectInput("IMAGE", "Sample image:",
                           list.files(path = "~",
                                      pattern = ".jpg",
                                      full.names = TRUE,
                                      include.dirs = FALSE))),

  fluidRow(

    plotOutput("IMG", click = "countClick", "100%", "500px")
  ),

  verbatimTextOutput("info")
)

server <- function(input, output, session){


  # Creating a reactive variable that recognizes the selected image
  img <- reactive({
    f <- input$IMAGE
    imager::load.image(f)
  })

  # Creating a spot where i can store reactive values
  initX <- 1
  initY <- 2

  source_coords <- reactiveValues(xy = c(x=initX,y=initY))

  # Coords
  dest_coords <- reactiveValues(x=initX, y = initY)
  observeEvent(plot_click(),{
    dest_coords$x <- c(dest_coords$x, floor(plot_click()$x))
    dest_coords$y <- c(dest_coords$y, floor(plot_click()$y))
  })

  plot_click <- debounce(reactive(input$countClick), 300)

  output$IMG <- renderPlot({
    plot(img(), axes = FALSE)
    n <- 0
    ex <- expression(n+1)
    text(dest_coords$x, dest_coords$y,eval(ex),cex = 1 ,col = 'red')
  })

  output$info <- renderPrint({
    req(input$countClick)
    x <- round(input$countClick$x,2)
    y <- round(input$countClick$y,2)
    cat("[", x, ", ", y, "]", sep = "")
  })
}

shinyApp(ui, server)

Answer 1

countClick is not a good name because input$countClick does not contain the numbers of clicks.

Not tested:

  numberOfClicks <- reactiveVal(0)
  dest_coords <- reactiveValues(x = initX, y = initY)
  observeEvent(plot_click(),{
    numberOfClicks(numberOfClicks() + 1)
    dest_coords$x <- c(dest_coords$x, floor(plot_click()$x))
    dest_coords$y <- c(dest_coords$y, floor(plot_click()$y))
  })

  plot_click <- debounce(reactive(input$countClick), 300)

  output$IMG <- renderPlot({
    plot(img(), axes = FALSE)
    n <- numberOfClicks()
    text(dest_coords$x, dest_coords$y, n, cex = 1 ,col = 'red')
  })