Shiny Leaflet map renders twice on switching input

leaflet

#1

Hi all, for full disclosure I've posted about this on Stack Overflow (linked) but haven't received a response that resolves the issue. I wonder if the RStudio Community can help.

I'm trying to produce a Shiny app with Leaflet that renders a choropleth map based on different input criteria. The map displays incidents of different types (input$type) and backgrounds (input$background). When additional types or backgrounds are specified, polygons are filled with updated incident data. It is working correctly with one snag. When I switch the date input from date range (input$dateInput) to presidential period (input$president), the choropleth for presidential period renders once, displaying polygons with no data, and then again with the polygons filled with the correct data for the pre-selected period ("President1"). How do I avoid the map rendering twice like this when the Presidency tab is pressed?

The raw data and shapefile used can be accessed here: https://github.com/cjbarrie/shiny_egy.

Working example:

Global:

library(shiny)
library(shinydashboard)
library(shinythemes)
library(leaflet)
library(rgdal)
library(rmapshaper)
library(sp)
library(dplyr)
library(lubridate)

wikiraw <-read.csv("~/wikisample_SO.csv")
shapefile <- readOGR("~/EGY_adm2.shp")
shapefile<-spTransform(shapefile, CRS("+init=epsg:4326"))
## Simplify shapefile to speed up rendering
shapefile <- ms_simplify(shapefile, keep = 0.01, keep_shapes = TRUE)
wikbounds<-bbox(shapefile)
wikiraw$incident_date <- as.Date(wikiraw$incident_date,
                                 format = "%m/%d/%Y")
wikiraw$presidency <- rep(NA, nrow(wikiraw))
wikiraw$incident_date1 <- as.numeric(wikiraw$incident_date)
wikiraw$event <- rep(1,nrow(wikiraw))
## Generate presidency categorical var.
wikiraw$presidency <- cut(wikiraw$incident_date1, 
                          breaks = c(-Inf, 15016, 15521, 15889, 16229, Inf), 
                          labels = c("President1", "President2", "President3", "President4", "President5"), 
                          right = FALSE)

Snippet of data.frame wikiraw:

  ID_2 incident_date incident_background incident_type presidency event
1  168    2013-11-26            Cultural         Group President4     1
2  133    2013-11-29            Cultural         Group President4     1
3  137    2014-01-25            Cultural         Group President4     1
4  168    2011-01-28            Cultural    Collective President1     1
5  168    2016-04-25            Cultural         Group President5     1
6  163    2015-02-08           Political    Individual President5     1

UI:

ui <- dashboardPage(
                    dashboardHeader(title = "Map tool"),
                    dashboardSidebar(sidebarMenu(menuItem("Map", tabName = "map"),
                                                 selectInput("input_type", "Date input type",
                                                             c("Date", "Presidency")),
                                                 uiOutput("dateSelect"),
                                                 uiOutput("typeSelect"),
                                                 uiOutput("backgroundSelect"),
                                                 uiOutput("presidentSelect"))),
                    dashboardBody(tabItems(
                      tabItem(tabName = "map",
                              leafletOutput("mymap", height=500)))))

Server:

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

  output$dateSelect <- renderUI({
    switch(input$input_type,
           "Date" = dateRangeInput("dateInput", "Dates:",
                                   min=min(wikiraw$incident_date), max = max(wikiraw$incident_date),
                                   start = min(wikiraw$incident_date), end = max(wikiraw$incident_date)),
           "Presidency" = checkboxGroupInput("president", "Presidency", 
                                             choices = levels(wikiraw$presidency),
                                             selected = "President1"))
  })

  output$typeSelect <- renderUI({
    selectInput("type", "Incident type", 
                choices = unique(wikiraw$incident_type), multiple = TRUE, 
                selected = wikiraw$incident_type[1])})

  output$backgroundSelect <- renderUI({
    checkboxGroupInput("background", "Incident background", 
                       choices = unique(wikiraw$incident_background),
                       selected = wikiraw$incident_background[1])})


  selected <- reactive({
    wikiagg <- wikiraw %>% group_by(ID_2, incident_date, incident_type, incident_background, presidency) %>%
      summarize(sum_event = sum(event))
    if(input$input_type=="Date"){wikiagg <- filter(wikiagg,
                                                   incident_date >= min(input$dateInput),
                                                   incident_date <= max(input$dateInput),
                                                   incident_type%in%input$type,
                                                   incident_background%in%input$background)}
    if(input$input_type=="Presidency"){wikiagg <- filter(wikiagg,
                                                         incident_type%in%input$type,
                                                         incident_background%in%input$background,
                                                         presidency%in%input$president)}

    wikiagg <- wikiagg %>% group_by(ID_2) %>%
      summarize(sum_event = sum(sum_event))
    wikiagg
  })

  output$mymap <- renderLeaflet({

    leaflet() %>% 
      addTiles() %>% 
      setView(mean(wikbounds[1,]),
              mean(wikbounds[2,]),
              zoom=6
      )
  })

  observe({
    if(!is.null(input$dateInput)){
      shapefile@data <- left_join(shapefile@data, selected(), by="ID_2")

      ##Define palette across range of data
      wikiaggpal <- wikiraw %>% group_by(ID_2) %>%
        summarize(sum_event = sum(event))
      pal <- colorBin("YlOrRd", wikiaggpal$sum_event, bins=5, na.color = "#bdbdbd")


      leafletProxy("mymap", data = shapefile) %>%
        addTiles() %>% 
        clearShapes() %>% 
        addPolygons(data = shapefile, fillColor = ~pal(sum_event), fillOpacity = 0.7, 
                    color = "white", weight = 2)
    }})
}
shinyApp(ui, server)

Gif of issue:

Any help would be hugely appreciated!