R and Leaflet: How to arrange label text across multiple lines

Question

Suppose you have the following data frame:

cities = data.frame( name = c('Madrid','Barcelona','Sevilla'),
                 country = c('Spain','Spain','Spain'),
                 region = c('Comunidad de Madrid','Cataluña','Andalucia'),
                 data = c(100, 200, 300), 
                 lng = c(-3.683333,2.166667,-6.083333),
                 lat = c(40.433333,41.383333,37.446667))

My idea is to have a map of these cities and labels that could display some relevant information when hovering the corresponding city circles. I'd like to have the label text arranged in several lines. The very first approach below failed:

library( leaflet )

map = leaflet( cities ) %>%
addTiles() %>%
addCircles( lng = ~lng, lat = ~lat, fillColor = 'darkBlue', radius = 10000, 
          stroke = FALSE, fillOpacity = 0.8, label = paste0( cities$name,'\n', cities$region, '\n', cities$country, '\n', cities$data ) )

as well as other similar attempts. After googling a while, I found a possible solution by involving the htmltools package:

library( htmltools )
map2 = leaflet( cities ) %>%
addTiles() %>%
addCircles( lng = ~lng, lat = ~lat, fillColor = 'darkBlue', radius = 10000, 
          stroke = FALSE, fillOpacity = 0.8, 
          label = HTML( paste0( '<p>', cities$name, '<p></p>', cities$region, ', ', cities$country,'</p><p>', cities$data, '</p>' ) ) )

In this case, the information is displayed as I'd like but, within the same label, there is an entry for each city of the dataset. How could I do to have the text of a single city arranged in multiple lines? Any help would be really appreciated

Answer 1

First, create a character vector of html content for each city and then wrap that in a lapply call to set the HTML attribute for correct display when defining the label attribute in adCircles

labs <- lapply(seq(nrow(cities)), function(i) {
  paste0( '<p>', cities[i, "name"], '<p></p>', 
          cities[i, "region"], ', ', 
          cities[i, "country"],'</p><p>', 
          cities[i, "data"], '</p>' ) 
})

map2 = leaflet( cities ) %>%
  addTiles() %>%
  addCircles(lng = ~lng, lat = ~lat, fillColor = 'darkBlue', radius = 10000, 
              stroke = FALSE, fillOpacity = 0.8,
              label = lapply(labs, htmltools::HTML))

map2

Answer 2

The following also works for two labels:

labels <- sprintf(
  "<strong>%s</strong><br/>%g people / mi<sup>2</sup>",
  states$name, states$density
) %>% lapply(htmltools::HTML)

m <- m %>% addPolygons(
  fillColor = ~pal(density),
  label = labels,
  labelOptions = labelOptions(
    style = list("font-weight" = "normal", padding = "3px 8px"),
    textsize = "15px",
    direction = "auto"))

m

see here for further info.

p.s: I wanted to use it for three labels but couldn't manage to.