Union of circles and polygon in leaflet

Question

I am adding two circles and a polygon to a leaflet map. Here\'s my code which plots these three shapes. Is there any way I can get a union of these three shapes?

Answer 1

I'd recommend moving away from spatial objects from the sp package and instead look at simple feature objects from the sf package.

Simple Features are the 'new' spatial class for R (and are made by the same guy who did sp).

So, to get the union of your circles, you can use

library(rgeos)
library(sf)


## A dataframe of your points
df <- data.frame(lon = c(ptTop1[1], ptTop2[1], ptBottom1[1], ptBottom2[1]),
                 lat = c(ptTop1[2], ptTop2[2], ptBottom1[2], ptBottom2[2]))

## convert them into a simple features data.frame
sf_df <- st_as_sf(df, coords = c("lon", "lat"))

## convert into circles
sf_circles <- st_buffer(sf_df, dist = 0.04)

## find the union of all the circles
sf_combined <- st_union(sf_circles)


## now sf_combined is a single polygon
sf_combined
# Geometry set for 1 feature 
# geometry type:  POLYGON
# dimension:      XY
# bbox:           xmin: 72.79573 ymin: 20.38366 xmax: 72.88561 ymax: 20.47837
# epsg (SRID):    NA
# proj4string:    NA
# POLYGON((72.8745460445306 20.4072956786729, 72....

As for plotting, leaflet can handle sf objects (except for MULTIPOINT), so you can plot it directly

library(leaflet)

sp <- as(sf_combined, 'Spatial')

sf_combined %>%
    leaflet() %>%
    addTiles() %>%
    addPolygons()