How to use a custom marker symbol in plotly scattermapbox for R

Question

I am currently developing a small shiny application that uses an interactive map. The idea is very simple: I am trying to plot a handful of points in a map using lat/long coordinates. I cannot use google's API, so I used plotly's scatter plot, specifying a map layout.

This is a generic representation of what I have so far:

fig <- plotly::plot_ly(
      data = data,
      lat = data$lat,
      lon = data$long,
      mode = "markers",
      marker = list(size = 10),
      type = 'scattermapbox',
      hovertext = paste0(
        paste0("Some info 1: ", data$field1, "\n"),
        paste0("Some info 2: ", data$field2, "\n"),
        paste0("Some info 3: ", data$field3)
        )
     )

# specify layout as open street map
fig <- fig %>%
      layout(
        mapbox = list(
          style = 'open-street-map',
          zoom = 3,
          center = list(lat = -20.72623, lon = -47.74942))
        ) 
    print(fig)

Considering that my "data" dataset has the fields and coordinates, the result I'm getting is this:

What I am not able to do is change the marker symbols. According to plotly's documentation (https://plotly.com/r/reference/#scatter-mode), it is as simple as defining symbol = "some_symbol", but that won't work. I've seen some examples and some workarounds, but none seem to work very intuitively.

Ideally, I wanted to generate a map that looked like this:

Does anyone know if this is even possible with a simple scatterplot? Is there any other way? Am I missing something here?

Answer 1

I found a solution for this, although using a different package.

Using the leaflet package, I was able to create a map using the same open-street-map layout. The default marker symbol/icon is a pin, but you can create any customized icon you want, using svg files. The leaflet documentation is specified here.

My specific solution was defining the hovertext as a set of labels and then simply calling the addMarkers function inside the leaflet object.

labels <- lapply(seq(nrow(data)), function(i) {
      paste0( '<p><b> Some information: ', data[i, "field1"], '</b></p>', 
              "<p> Some other information : ", data[i, "field2"] / 1000, ' MWm </p>', 
              "<p> Some different information : ", data[i, "field3"],'</p>')
    })
    
fig <- leaflet::leaflet(data = data) %>% leaflet::addTiles() %>%
       leaflet::addMarkers(
        ~as.numeric(longitude),
        ~as.numeric(latitude),
        label = lapply(labels, htmltools::HTML)
       )
       print(fig)