"Preselecting" shapes on leaflet map shiny using mapedit::selectmod

Date: Sun, 25 Mar 2018 23:14:36 +1100
From: nevil amos <nevil.amos at gmail.com>
To: r-sig-geo at r-project.org
Subject: [R-sig-Geo] Fwd: "Preselecting" shapes on leaflet map shiny
        using mapedit::selectmod

Tahnks,

I have adapted your code a litle to get further towards what I need., could
not work out how to respond on the git gist site so sending to you direct.

I have now set up the app so that it initially shows the preselected
polygons, but does not allow clicking to change the selection.    changing
the radio button "turns on" the selection,  but when I change the button
back to no it does not trun it off again.  how do I trun of the
map_shape_click again?

thanks again for your help


# Draw a map which responds to clicks by toggling the selection state
# of the clicked polygon.
library(shiny)
library(leaflet)
library(sf)

nc=st_as_sf(gadmCHE)
nc$selected<-0
# Initial selection
nc$selected[nc$NAME_1%in%c("Aargau", "Appenzell Ausserrhoden", "Appenzell
Innerrhoden",
                           "Basel-Landschaft", "Basel-Stadt", "Bern",
"Fribourg")]<-1
ui <- fluidPage(
  titlePanel("Leaflet selection demo"),
  radioButtons(inputId = "selectable",label = "allow selection by
clicking?",choiceNames = c("no","yes"),choices =  c("no","yes")),
  leafletOutput('map')
)

server <- function(input, output) {
  output$map = renderLeaflet({
    leaflet() %>% addTiles() %>%
      addPolygons(data=nc, fillColor=~c('red', 'blue')[selected+1],
                  layerId=~NAME_1,
                  label=~NAME_1)
  })
  observe({
    if (input$selectable=="yes"){
      observeEvent(input$map_shape_click, ignoreInit=TRUE, {
        id = input$map_shape_click$id
        map = leafletProxy('map') %>%
          removeShape(id)

        nc_local = nc
        ix = which(nc_local$NAME_1==id)
        nc_local$selected[ix] = 1 - nc_local$selected[ix]
        nc <<- nc_local

        map %>% addPolygons(data=nc_local[ix,], fillColor=~c('red',
'blue')[selected+1],
                            layerId=id)
      })
    }else{
      #make the map  not selectable
    }
  }
  )

  xx<<-nc[nc$selected==1]
}

shinyApp(ui = ui, server = server)