function for adding a scaled circle legend to a leaflet map in R

addBubbleLegend.R

addBubbleLegend <- function(
  map, title = "", range, scaling_fun, ...,
  strokeColor, weight, fillColor, fillOpacity,
  position = c("topright", "bottomright", "bottomleft", "topleft"),
  data = getMapData(map), layerId = NULL
) {
  range <- base::pretty(sort(range), 20)
  range <- range[range != 0]
  min_n <- min(range, na.rm = TRUE)
  med_n <- median(range, na.rm = TRUE)
  max_n <- max(range, na.rm = TRUE)
  n_range <- c(min_n, med_n,  max_n)
  radii <- scaling_fun(n_range, ...)
  
  circle_style <- glue::glue(
     	"border-radius:50%;
    	border: {weight}px solid {strokeColor};
    	background: {paste0(fillColor, round(fillOpacity*100, 0))};
    	position: absolute;
      	bottom:1px;
      	right:25%;
      	left:50%;"
  )
  
  text_style <-
     	"text-align: right;
      	font-size: 11px;
    	position: absolute;
    	bottom: 0px;
      	right:1px;"
  
  circle_legend <- HTML(glue(
    '<div class="bubble-legend">
    	<div id="legendTitle" style="text-align: center; font-weight: bold;">{title}</div>
    	<div class="symbolsContainer" style="min-width: {radii[3]*2 + 25}px; min-height: {radii[3]*2}px;">
    		<div class="legendCircle" style="width: {radii[1] * 2}px; height: {radii[1] * 2}px; margin-left: {-radii[1]}px; {circle_style}"></div>
    		<div class="legendCircle" style="width: {radii[2] * 2}px; height: {radii[2] * 2}px; margin-left: {-radii[2]}px; {circle_style}"></div>
    		<div class="legendCircle" style="width: {radii[3] * 2}px; height: {radii[3] * 2}px; margin-left: {-radii[3]}px; {circle_style}"></div>
    		<div><p class="legendValue" style="margin-bottom: {radii[1] * 2 - 12}px; {text_style}">{n_range[1]}</p></div>
		<div><p class="legendValue" style="margin-bottom: {radii[2] * 2 - 12}px; {text_style}">{n_range[2]}</p></div>
    		<div><p class="legendValue" style="margin-bottom: {radii[3] * 2 - 12}px; {text_style}">{n_range[3]}</p></div>
    	</div>
    </div>'
  ))
  
  return(
    addControl(map, html = circle_legend, position = position, layerId = layerId)
  )
}