如何保存之前的无功值？

Question

如何在 R闪亮中保存以前的无功值？我想提取最后两个标记位置的坐标（传单）。我尝试使用隔离功能（没有成功）。在当前形式中，我的代码可以存储当前的反应变量，但无法存储最后一个。

这是我的代码：

# Define UI 
ui <- fluidPage(
  leafletOutput("mymap",height=800)
)

# Define server logic 
server <- function(input, output) {
  
  # Leaflet
  output$mymap <- renderLeaflet(
    leaflet() %>%
      addTiles() %>%
      setView(lng = 8.53918, lat = 47.36864, zoom = 11) %>%
      addDrawToolbar(
        targetGroup='draw',
        polylineOptions = F,
        polygonOptions = F,
        rectangleOptions = F,
        circleOptions = F,
        circleMarkerOptions = F,
        editOptions = editToolbarOptions(selectedPathOptions = selectedPathOptions()))  %>%
      addLayersControl(overlayGroups = c('draw'), options =
                         layersControlOptions(collapsed=FALSE))
  )
  
  reactive({
    
    PosData <- data.frame(PosX = c(NA,NA),
                          PosY = c(NA,NA),
                          PosDegree = c(NA,NA))
    
  })
 
  
  # Extract coordinates
  observeEvent(input$mymap_draw_new_feature,{
    if(input$mymap_draw_new_feature$geometry$type == "Point"){

      PosData$PosX[1] <- input$mymap_draw_new_feature$geometry$coordinates[[1]]
      PosData$PosY[1] <- input$mymap_draw_new_feature$geometry$coordinates[[2]]
      
      PosData$PosX[2] <- PosData$PosX[1]
      PosData$PosY[2] <- PosData$PosY[1]
      
      print(PosData)

    }else{f <- 2}

  })
}

# Run the application
shinyApp(ui = ui, server = server)```

Answer 1

在此应用程序中，反应表

PosData

将包含最后 2 个标记的位置：

library(shiny)
library(leaflet)
library(leaflet.extras)
library(tidyverse)

ui <- fluidPage(
  leafletOutput("mymap", height = 800),
  tableOutput("PosData")
)

# Define server logic
server <- function(input, output) {

  # Leaflet
  output$mymap <- renderLeaflet(
    leaflet() %>%
      addTiles() %>%
      setView(lng = 8.53918, lat = 47.36864, zoom = 11) %>%
      addDrawToolbar(
        targetGroup = "draw",
        polylineOptions = F,
        polygonOptions = F,
        rectangleOptions = F,
        circleOptions = F,
        circleMarkerOptions = F,
        editOptions = editToolbarOptions(selectedPathOptions = selectedPathOptions())
      ) %>%
      addLayersControl(
        overlayGroups = c("draw"), options =
          layersControlOptions(collapsed = FALSE)
      )
  )

  PosData <- reactiveVal(value = tibble(PosX = numeric(), PosY = numeric()))

  output$PosData <- renderTable(PosData())

  # Extract coordinates
  observeEvent(input$mymap_draw_new_feature, {
    req(input$mymap_draw_new_feature$geometry$type == "Point")

    PosData() %>%
      add_row(
        PosX = input$mymap_draw_new_feature$geometry$coordinates[[1]],
        PosY = input$mymap_draw_new_feature$geometry$coordinates[[2]]
      ) %>%
      # keep last 2 points
      tail(2) %>%
      PosData()
  })
}

# Run the application
shinyApp(ui = ui, server = server)