library(sf)
library(tmap)
library(tidyverse)
library(leaflet)
library(stringi)

mean_lat <- 43.9
sd_lat <- 0.1
mean_long <- -79.384293
sd_long <-  0.1

set.seed(42)
trees <- data.frame(lat = rnorm(500, mean = mean_lat, sd = sd_lat),
                      long = rnorm(500, mean = mean_long, sd = sd_long))

trees <- mutate(trees, tree_type = stri_rand_strings(500, 1, pattern = "[A-I]"))

radius = 500

# Convert to sf, set the crs to EPSG:4326 (lat/long),
# and transform CRS to Lambert conformal conic projection - North America
tree_sf <- st_as_sf(trees, coords = c("long", "lat"), crs = 4326) %>%
  st_transform(102009)

# Buffer circles by 100m
tree_circles <- st_buffer(tree_sf, dist = radius)
enclosed_trees <- st_intersection(tree_sf, tree_circles)

# Transform back to 4326 to make Leaflet happy
tree_circles <- st_transform(tree_circles, 4326)
enclosed_trees <- st_transform(enclosed_trees,4326)

leaflet() %>%
  addTiles() %>%
  addPolygons(data = tree_circles) %>%
  addCircles(data = enclosed_trees)