How to implement labels that only refer to the current location for spot icons?

I am using the following df:

df <- structure(list(name = c("name1", "name2", "name3", "name4"), 
    postcode = c("NE6 4AG", "YO12 4HG", "N1 2SR", "CR4 3SR"), 
    type = c("type1", "type1", "type1", "type2"), lat = c(54.9849, 
    54.26435, 51.53963, 51.402), long = c(-1.56043, -0.41642, 
    -0.09786, -0.1743)), row.names = c(NA, -4L), class = c("tbl_df", 
"tbl", "data.frame"))

I am getting labels for each location that contain information on all locations.

How to make labels that contain information only on the single site it refers to?

I am using the following script:

library(leaflet)
library(htmlwidgets)
library(dplyr)
library(tidygeocoder)
library(leaflet.extras)  
library(htmltools)  

# Define colors for site types
site_colors <- c("type1" = "red", "type2" = "blue")

# Define custom icons for the markers
type1_icon <- makeIcon(
  iconUrl = "https://raw.githubusercontent.com/pointhi/leaflet-color-markers/master/img/marker-icon-red.png",
  iconWidth = 25, iconHeight = 41,
  iconAnchorX = 12, iconAnchorY = 41
)

type2_icon <- makeIcon(
  iconUrl = "https://raw.githubusercontent.com/pointhi/leaflet-color-markers/master/img/marker-icon-blue.png",
  iconWidth = 25, iconHeight = 41,
  iconAnchorX = 12, iconAnchorY = 41
)

# Split the data into two subsets
type1df <- df %>% filter(type == "type1")
type2df <- df %>% filter(type == "type2")

# Create the leaflet map
map <- leaflet() %>%
  addTiles() %>%  # Add default OpenStreetMap tiles
  
  # Add markers for type1 sites with the red icon
  addMarkers(
    data = type1df,
    lng = ~long,
    lat = ~lat,
    icon = type1_icon,
    label = ~htmltools::HTML(
      paste(
        "<strong>", name, "</strong><br>",
        postcode
      )
    ),
    labelOptions = labelOptions(
      noHide = TRUE,  # Makes the label always visible
      direction = "top",
      opacity = 0.8,
      textsize = "12px"
    )
  ) %>%
  
  # Add markers for type2 sites with the blue icon
  addMarkers(
    data = type2df,
    lng = ~long,
    lat = ~lat,
    icon = type2_icon,
    label = ~htmltools::HTML(
      paste(
        "<strong>", name, "</strong><br>",
        postcode
      )
    ),
    labelOptions = labelOptions(
      noHide = TRUE, 
      direction = "auto",  
      opacity = 0.8,  
      textsize = "12px"  
    )
  ) %>%
  # Add legend
  addLegend(
    "bottomright",
    colors = c("red", "blue"),
    labels = c("type1", "type2"),
    title = "Site Type"
  )

Solution

You can use lapply to generate the labels with the single current location information:

label = lapply(
    paste("<strong>", type2df$name, "</strong><br>", type2df$postcode), 
    htmltools::HTML
)

library(leaflet)

df <- structure(list(name = c("name1", "name2", "name3", "name4"), 
                     postcode = c("NE6 4AG", "YO12 4HG", "N1 2SR", "CR4 3SR"), 
                     type = c("type1", "type1", "type1", "type2"), lat = c(54.9849, 
                                                                           54.26435, 51.53963, 51.402), long = c(-1.56043, -0.41642, 
                                                                                                                 -0.09786, -0.1743)), row.names = c(NA, -4L), class = c("tbl_df", 
                                                                                                                                                                        "tbl", "data.frame"))

# Define colors for site types
site_colors <- c("type1" = "red", "type2" = "blue")

# Define custom icons for the markers
type1_icon <- makeIcon(
  iconUrl = "https://raw.githubusercontent.com/pointhi/leaflet-color-markers/master/img/marker-icon-red.png",
  iconWidth = 25, iconHeight = 41,
  iconAnchorX = 12, iconAnchorY = 41
)

type2_icon <- makeIcon(
  iconUrl = "https://raw.githubusercontent.com/pointhi/leaflet-color-markers/master/img/marker-icon-blue.png",
  iconWidth = 25, iconHeight = 41,
  iconAnchorX = 12, iconAnchorY = 41
)

# Split the data into two subsets
type1df <- df[df$type == "type1", ]
type2df <- df[df$type == "type2", ]

# Create the leaflet map
leaflet() |> 
  addTiles() |>   # Add default OpenStreetMap tiles
  
  # Add markers for type1 sites with the red icon
  addMarkers(
    data = type1df,
    lng = ~long,
    lat = ~lat,
    icon = type1_icon,
    label = lapply(
      paste("<strong>", type1df$name, "</strong><br>", type1df$postcode), 
      htmltools::HTML
    ),
    labelOptions = labelOptions(
      noHide = TRUE,  # Makes the label always visible
      direction = "top",
      opacity = 0.8,
      textsize = "12px"
    )
  ) |> 
  
  # Add markers for type2 sites with the blue icon
  addMarkers(
    data = type2df,
    lng = ~long,
    lat = ~lat,
    icon = type2_icon,
    label = lapply(
      paste("<strong>", type2df$name, "</strong><br>", type2df$postcode), 
      htmltools::HTML
    ),
    labelOptions = labelOptions(
      noHide = TRUE, 
      direction = "auto",  
      opacity = 0.8,  
      textsize = "12px"  
    )
  ) |> 
  # Add legend
  addLegend(
    "bottomright",
    colors = c("red", "blue"),
    labels = c("type1", "type2"),
    title = "Site Type"
  )