[R-sig-Geo] "Preselecting" shapes on leaflet map shiny using mapedit::selectmod

[Kent Johnson]

>
> 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?
>

Remove the observe() and put the check for input$selectable inside
observeEvent(). If the input is not selectable then you ignore the click
event; if it is selectable then you handle the click. You don't need to
respond directly to changes in input$selectable.


> 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)

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