Combining Spatial Dataframes with different columns

Question

I have three different spatial dataframes that I'm trying to combine as one big one. The reproducible code looks like this:

library(sf)
library(sp)
library(leaflet)
library(tigris)
library(rgdal)
library(raster)
library(dplyr)


# Dataset 1 ---------------------------------------------------------------

set1 <- voting_districts("nevada") 
set1 <- subset(set1,set1$COUNTYFP10 != '003')
set1 <- subset(set1,set1$COUNTYFP10 != '031')

# Dataset 2 ---------------------------------------------------------------

#Dataset Download Link:
#https://opendata.arcgis.com/datasets/3e738fdaca2b4aeba0c18a2478cae956_0.zip?outSR=%7B%22wkid%22%3A102707%2C%22latestWkid%22%3A3421%7D

dsn <- "./Precincts"
set2 = readOGR(dsn)


# Dataset 3 ---------------------------------------------------------------

#Dataset Download Link:
#https://opendata.arcgis.com/datasets/fcab7fcd0b2e4243b4f6d7292c2e4daa_7.zip?outSR=%7B%22latestWkid%22%3A3423%2C%22wkid%22%3A102709%7D

dsn <- "./Voter_Districts"
set3 = readOGR(dsn)


# Transform ---------------------------------------------------------------

set1 <- spTransform(set1, CRS("+init=epsg:4326"))
set2 <- spTransform(set2, CRS("+init=epsg:4326"))
set3 <- spTransform(set3, CRS("+init=epsg:4326"))


# Plot --------------------------------------------------------------------

leaflet() %>%
  addProviderTiles("CartoDB.Positron") %>%
  addPolygons( fillColor = "red",
               color = "black",
               weight = 1.0, data = set1) %>%
  addPolygons( fillColor = "blue",
               color = "black",
               weight = 1.0, data = set2) %>%
  addPolygons(fillColor = "green",
              color = "black",
              weight = 1.0, data = set3)

What I would like to do is combine them all into one big SpatialPolygonsDataFrame that would allow me to do the same plot as above, but without the need for two additional addPolygons functions. Something like this:

leaflet(combined_sets) %>%
  addProviderTiles("CartoDB.Positron") %>%
  addPolygons(...)

Is that even possible? Given that they are three different datasets with different columns, I'm not sure if it can be done.

Answer 1

As said in the comment, there are soltions. Both bindand raster::unionworked for me

ab <- bind(set2,set3)
ab <- raster::union(set2,set3)

leaflet() %>%
  addProviderTiles("CartoDB.Positron") %>%
  addPolygons( fillColor = "blue",
               color = "black",
               weight = 1.0, data = ab)