R: Add title to Leaflet map

问题:

I'd like to add a title to the whole map (different from the legend title: addLegend(..., title = "", ...): by "title", I mean an overlaid map component that stays in place while the map is moved (unlike an overlaid image).

Is that an option in RStudio's leaflet for R?

leafletR has a title="" argument but it updates the title of the webpage: it does not add a title to the map.

回答1:

You should provide a reproducible example. But using addControl you could try:

 library(leaflet)
 library(htmlwidgets)
 library(htmltools)

 rr <- tags$div(
   HTML('<a href="https://cran.r-project.org/"> <img border="0" alt="ImageTitle" src="/PathToImage/ImageR.jpeg" width="300" height="100"> </a>')
 )  

 map_leaflet <- leaflet() %>%
   addTiles() %>%
   addMarkers(50, 50) %>%
   addControl(rr, position = "bottomleft")

 saveWidget(map_leaflet, file="testing.html")

Open testing.html saved in your working directory and you will see an image (just create an image with Map Title in it) over your map. It is not center you can only put the control on the four corners. Hope it helps!

回答2:

@MLavoie's idea is correct, but I was looking for something more specific like this:

tag.map.title <- tags$style(HTML("
  .leaflet-control.map-title { 
    transform: translate(-50%,20%);
    position: fixed !important;
    left: 50%;
    text-align: center;
    padding-left: 10px; 
    padding-right: 10px; 
    background: rgba(255,255,255,0.75);
    font-weight: bold;
    font-size: 28px;
  }
"))

title <- tags$div(
  tag.map.title, HTML("Map title")
)  

map_leaflet <- leaflet() %>%
  addTiles() %>%
  addControl(title, position = "topleft", className="map-title")

This will center the leaflet-control title as shown in the screenshot and place it at the top.