coloring polygons in ggplot2 (R)

Question

I am very new to R. I managed to produce the below map with the code below.

I want to color the the rightmost polygon on the map (denoted "WestTerr" in the code) a different color than the other three polygons (denoted "Serena" in the code). I have tried various things that have all thrown errors at me. Does anyone know how to help me?

library(ggmap)
library(RgoogleMaps)
library(foreign)
library(raster)
library(sp)
library(rgeos)
library(spatstat)
library(maptools)
library(rgdal)
library(ggplot2)

CenterOfMap <- geocode("-1.4, 35.08")

MasaiMara <- get_map(c(lon=CenterOfMap$lon, lat=CenterOfMap$lat), zoom = 10, 
                     maptype = "roadmap", source = "google")

MasaiMaraMap <- ggmap(MasaiMara)

setwd("Territories_Jenna/")

SouthTerr <- readOGR(".","SouthMCP")
SouthTerr <- spTransform(SouthTerr, CRS("+proj=longlat +datum=WGS84"))
fortify(SouthTerr)

HZTerr <- readOGR(".","HZMCP")
HZTerr <- spTransform(HZTerr, CRS("+proj=longlat +datum=WGS84"))
fortify(HZTerr)

SandHZ <- gUnion(SouthTerr, HZTerr)
SandHZ <- spTransform(SandHZ, CRS("proj=longlat +datum=WGS84"))
fortify(SandHZ)

MapwithSandHZ <- MasaiMaraMap +
                 geom_polygon(aes(x=long, y=lat, group=group),
                              fill = "black", size=.7, color="black",
                              data=SandHZ, alpha=0)

NorthTerr <- readOGR(".","NorthMCP")
NorthTerr <- spTransform(NorthTerr, CRS("+proj=longlat +datum=WGS84"))
fortify(NorthTerr)

MapwithNorth <- MasaiMaraMap +
                geom_polygon(aes(x=long, y=lat, group=group),
                             fill = "black", size=.7, color="black",
                             data=NorthTerr, alpha=0)

Serena <- gUnion(SandHZ, NorthTerr)
Serena <- spTransform(Serena, CRS("proj=longlat +datum=WGS84"))
fortify(Serena)

MapwithSerena <- MasaiMaraMap +
                 geom_polygon(aes(x=long, y=lat, group=group),
                              fill = "black", size=.7, color="black",
                              data=Serena, alpha=0)

WestTerr <- readOGR(".","WestMCP")
WestTerr <- spTransform(WestTerr, CRS("+proj=longlat +datum=WGS84"))
fortify(WestTerr)

MapwithWest <- MasaiMaraMap +
               geom_polygon(aes(x=long, y=lat, group=group), 
                            fill = "red", size=.7, color="red",
                            data=WestTerr, alpha=0)

AllTerrs <- gUnion(Serena, WestTerr)
AllTerrs <- spTransform(AllTerrs, CRS("proj=longlat +datum=WGS84"))
fortify(AllTerrs)

MapwithAllTerrs <- MasaiMaraMap +
                   geom_polygon(aes(x=long, y=lat, group=group),
                                fill = "red", size=.7, color="red",
                                data=AllTerrs, alpha=0)

MapwithAllTerrs

Answer 1

I do not have access to your data, so I created a sample data. Seeing your code, you created four polygons in four calls. I think you want to combine all data and draw polygons. When you use fortify(), you see a column for id. You want to make sure that each polygon has a unique ID, if you combine your data. Once you have the data, you can do your work straightforward, I think. You can manually change the colors of polygons with scale_fill_manual()

library(ggmap)
CenterOfMap <- geocode("-1.4, 35.08")

MasaiMara <- get_map(c(lon=CenterOfMap$lon, lat=CenterOfMap$lat), zoom = 10, 
                     maptype = "roadmap", source = "google")
                 
ggmap(MasaiMara) +
geom_polygon(data = mydf, aes(x = long, y = lat, group = id, fill = factor(id))) +
scale_fill_manual(values = c("red", "red", "blue"))

DATA

mydf <-structure(list(id = c(1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 
3L, 3L, 3L, 3L, 3L), long = c(34.97, 34.95, 34.95, 34.97, 34.97, 
35, 34.82, 34.83, 35, 35, 35.2, 35.1, 35.1, 35.2, 35.2), lat = c(-1.38, 
-1.38, -1.4, -1.4, -1.38, -1.6, -1.6, -1.7, -1.7, -1.6, -1.43, 
-1.43, -1.5, -1.5, -1.43)), class = c("tbl_df", "tbl", "data.frame"
), row.names = c(NA, -15L), .Names = c("id", "long", "lat"), spec = structure(list(
cols = structure(list(id = structure(list(), class = c("collector_integer", 
"collector")), long = structure(list(), class = c("collector_double", 
"collector")), lat = structure(list(), class = c("collector_double", 
"collector"))), .Names = c("id", "long", "lat")), default = structure(list(), class = c("collector_guess", 
"collector"))), .Names = c("cols", "default"), class = "col_spec"))