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

[Kent Johnson]

Here is a minimal example:

https://gist.github.com/kent37/63c55c0bbdb0640d8c43369cdeeebdd2



Kent

On Thu, Mar 22, 2018 at 9:11 AM, Kent Johnson <kent3737 at gmail.com> wrote:

> On Thu, Mar 22, 2018 at 7:00 AM, <r-sig-geo-request at r-project.org> wrote:
>>
>> Message: 1
>> Date: Thu, 22 Mar 2018 12:37:00 +1100
>> From: nevil amos <nevil.amos at gmail.com>
>> To: r-sig-geo at r-project.org
>> Subject: [R-sig-Geo] "Preselecting" shapes on leaflet map shiny using
>>         mapedit::selectmod
>>
>> Hi I  am  putting together a shiny map app in which I want to allow for
>> selection or deselection of polygons from  a map layer.
>> Importantly At the beginning of the process I would like a subset of the
>> polygons to be already selected ( and they can then be deselected using a
>> click if required).
>> The final set of selected polygons is then saved to disk.
>>
>> Ideally I would like to be able ( eg using a shiny action button) to reset
>> the selection to the pre-selected polygons.
>
>
> I did something very similar to this using just leaflet and shiny (no
> mapedit). I was drawing many polygons and wanted to change the state of a
> polygon based on a click.
>
> I don't have the code handy, but basically it was
> - create an initial map drawing the polygons with the desired initial
> state. Use a unique layerId for each polygon.
> - listen to input$map_shape_click with observeEvent. On click, remove the
> clicked polygon from the map with leaflet::removeShape(leafletProxy('map',
> input$map_shape_click$layerId), change the state of the polygon, and add
> it back to the map.
>  - Save the state when a "Save" button is clicked.
>
> If there are polygons you don't want to respond to clicks, you will have
> to filter them out in the click handler using layerId.
>
> See the Inputs/Events section of the leaflet docs here for more
> information: https://rstudio.github.io/leaflet/shiny.html
>
> HTH,
> kent
>

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