How To make hideGroup into showGroup with Shiny and Leaflet

I have a fairly complex Shiny app with a leaflet map on it and many other controls. I have made a very simplified version of it below.

I have set the two groups (an addMarker and an addCircles group) initially to not plot by placing both layers in a hideGroup function. I then run the app and manually switch them on in the addLayersControl in the checkbox on the map. The radius of the addCircles group is controlled reactively by a sliderInput, however, this then runs the hideGroup functions again and they are not plotted, which I now do not want to happen. I want them to remain plotted.

How do I start off with hidden groups, show them by switching them on via the map layer control and then send a new value to the addCirlces radius without the groups then switching back to the hidegroup default please?

Do I tackle the problem with isolate, I haven’t had any success that way yet? Or is there an if_else conditional approach I should take to invoke a showGroup state instead? Thanks in advance.

library(shiny)
library(tidyverse)
library(leaflet)
library(sf)

ui <- fluidPage(
  column(width = 4,
         sliderInput("slt_kam_reach",
                     "KAM",
                     min = 0,
                     max = 50000,
                     step = 1000,
                     value = 5000
         )
         ),
  column(width = 8,
     leafletOutput("lflt_map")
     )
)

kam_data <- data.frame(
  kam_code = c("abc123", "def456"),
  lng = c(18.5, 18.7),
  lat = c(-33.5, -33.7)
)

kam_data_sf <- st_as_sf(
    kam_data,
    coords = c("lng", "lat"),
    crs = "+proj=longlat +datum=WGS84"
  )

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

  output$lflt_map <- renderLeaflet({

    leaflet() %>% 
      addTiles(group = "OSM") %>% 
      addLayersControl(
        overlayGroups = c("KAM",
                          "KAM_reach"),
        options = layersControlOptions(
          collapsed = F
        )
      ) %>% 
      addMarkers(data = kam_data_sf,
                 group = "KAM") %>% 
      addCircles(data = kam_data_sf,
                 group = "KAM_reach",
                 radius = input$slt_kam_reach
                 ) %>% 
      hideGroup("KAM") %>% 
      hideGroup("KAM_reach")

  })
}
shinyApp(ui, server)

I see you posted an answer as I finished mine. Here it is anyway:

library(shiny)
library(tidyverse)
library(leaflet)
library(sf)

ui <- fluidPage(
  column(width = 4,
         sliderInput("slt_kam_reach",
                     "KAM",
                     min = 0,
                     max = 50000,
                     step = 1000,
                     value = 5000
         )
         ),
  column(width = 8,
     leafletOutput("lflt_map")
     )
)

kam_data <- data.frame(
  kam_code = c("abc123", "def456"),
  lng = c(18.5, 18.7),
  lat = c(-33.5, -33.7)
)

kam_data_sf <- st_as_sf(
    kam_data,
    coords = c("lng", "lat"),
    crs = "+proj=longlat +datum=WGS84"
  )

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

  output$lflt_map <- renderLeaflet({

    leaflet() %>% 
      addTiles(group = "OSM") %>% 
      addLayersControl(
        overlayGroups = c("KAM",
                          "KAM_reach"),
        options = layersControlOptions(
          collapsed = F
        )
      ) %>% 
      hideGroup("KAM") %>% 
      hideGroup("KAM_reach") %>% 
      fitBounds(min(kam_data$lng),
                min(kam_data$lat),
                max(kam_data$lng),
                max(kam_data$lat))      

  })

  observeEvent(input$slt_kam_reach, {
      leafletProxy("lflt_map") %>% 
          clearGroup("KAM_reach") %>% 
          addMarkers(data = kam_data_sf,
                 group = "KAM") %>% 
          addCircles(data = kam_data_sf,
                 group = "KAM_reach",
                 radius = input$slt_kam_reach
                 )
  })
}
shinyApp(ui, server)

Update

You could use an observe as well which is probably neater:

  observe({
      leafletProxy("lflt_map") %>% 
          clearGroup("KAM_reach") %>% 
          addMarkers(data = kam_data_sf,
                 group = "KAM") %>% 
          addCircles(data = kam_data_sf,
                 group = "KAM_reach",
                 radius = input$slt_kam_reach
                 )
  })