Click on leaflet marker and get info - r

Question

Based on the comments below I've explicitly broken out lat/long in the spatial data frame.
Added
addCircleMarkers( ~ longitude, ~ latitude)
Added
observeEvent(input$map_marker_click, {
p <- input$map_marker_click
print(p)
})
Yet, nothing shows up in the console when I click the markers so I'm still confused.
Revised Code
# Click on circle and get info
library(shiny)
library(leaflet)
ui <- fluidPage(
leafletOutput("mymap"),
fluidRow(verbatimTextOutput("click_text"))
)
server <- function(input, output, session) {
# Create tree geometries
tree_1g <- st_point(c(-79.2918671415814, 43.6760766531298))
tree_2g <- st_point(c(-79.4883669334101, 43.6653747165064))
tree_3g <- st_point(c(-79.2964680812039, 43.7134458013647))
# Create sfc object with multiple sfg objects
points_sfc <- st_sfc(tree_1g, tree_2g, tree_3g, crs = 4326)
# Create tree attributes
data <- data.frame (
layerId = c("001", "002", "003"),
address = c(10, 20, 30),
street = c("first", "second", "third"),
tname = c("oak", "elm", "birch"),
latitude = c(43.6760766531298, 43.6653747165064, 43.7134458013647),
longitude = c(-79.2918671415814, -79.4883669334101, -79.2964680812039)
)
tree_data <- st_sf(data, geometry = points_sfc)
output$mymap <- renderLeaflet({
leaflet(data = tree_data) %>%
addProviderTiles(providers$Stamen.Watercolor) %>%
# Centre the map in the middle of Toronto
setView(lng = -79.384293,
lat = 43.685,
zoom = 11) %>%
addCircleMarkers( ~ longitude, ~ latitude)
})
observeEvent(input$map_marker_click, {
p <- input$map_marker_click
print(p)
})
}
shinyApp(ui, server)
When a user clicks on each marker I would like some relevant info displayed below the map. Based on this earlier post I tried this. However, nothing happens when I click on the marker. It may have something to do with my not understanding how to associate markers with layerIds?
# Click on circle and get info
library(shiny)
library(leaflet)
ui <- fluidPage(
leafletOutput("mymap"),
fluidRow(verbatimTextOutput("click_text"))
)
server <- function(input, output, session) {
# Create tree geometries
tree_1g <- st_point(c(-79.2918671415814, 43.6760766531298))
tree_2g <- st_point(c(-79.4883669334101, 43.6653747165064))
tree_3g <- st_point(c(-79.2964680812039, 43.7134458013647))
# Create sfc object with multiple sfg objects
points_sfc <- st_sfc(tree_1g, tree_2g, tree_3g, crs = 4326)
# Create tree attributes
data <- data.frame (
layerId = c("001", "002", "003"),
address = c(10, 20, 30),
street = c("first", "second", "third"),
tname = c("oak", "elm", "birch")
)
tree_data <- st_sf(data, geometry = points_sfc)
output$mymap <- renderLeaflet({
leaflet(data = tree_data) %>%
addProviderTiles(providers$Stamen.Watercolor) %>%
# Centre the map in the middle of Toronto
setView(lng = -79.384293,
lat = 43.685,
zoom = 11) %>%
addCircleMarkers()
})
observe({
click <- input$map_marker_click
if(is.null(click))
return()
address <- paste("Address: ", click$street)
output$click_text <- renderText({
address
})
})
}
shinyApp(ui, server)

Answer 1

When you 'observe' something on the map, you need to reference the map you're observing. You do this using this structure
output$<map_id>_event_to_observe
So, in your example your map_id is mymap, hence you'll need to use
observeEvent(input$mymap_marker_click, {
p <- input$mymap_marker_click
print(p)
})