A sample for plotting density map

This is a sample plot for visualizing high volume density area

SHA_1214_Stop_GPS <- read.csv("C:/Users/AEE1GSS/Desktop/0311/SHA_DRIVERMAP/SHA_1214_Stop_GPS.csv")
library(ggplot2)
library(ggmap)
library(mapproj)

## Loading required package: maps

SHA_MAP_zoom12 <- ggmap(get_map(maptype = "terrain", location = "shanghai", 
    zoom = 12, source = "google"), base_layer = ggplot(aes(x = Longitude, y = Latitude), 
    data = SHA_1214_Stop_GPS), extent = "panel")

SHA_MAP_zoom12 + stat_density2d(aes(x = Longitude, y = Latitude, fill = ..level.., 
    alpha = ..level..), size = 2, bins = 5, data = SHA_1214_Stop_GPS, geom = "polygon") + 
    scale_alpha(range = c(0.4, 0.75), guide = FALSE) + scale_fill_gradient(limits = c(0, 
    200))

## Warning: Removed 1105 rows containing non-finite values (stat_density2d).