我有洛杉矶港地区的颗粒物浓度差异(之后 - 之前)。我正在尝试使用 ggmap 在地图上绘制浓度等高线,但结果看起来很不同。我使用的代码如下所示(数据在代码下方):
代码
install.packages('ggmap')
library(ggmap)
PM = read.csv('data.csv', stringsAsFactors = FALSE)
获取经度和纬度
geocode("Port of Los Angeles") # Not centered
geocode("Compton, CA") # Now centered
使用康普顿 LON 和 LAT
POLA = c(lon = -118.220071, lat = 33.895849)
POLA.map = get_map(location = POLA, zoom = 10, color = 'bw')
ggmap(POLA.map) + geom_point(data = PM, mapping = aes(Longitude, Latitude)) +
stat_density2d(data = PM, mapping = aes(x = Longitude, y = Latitude, fill=..level..), geom = "polygon", alpha = 0.3, contour = TRUE)
但是,等高线图应该有这样的模式:
https://drive.google.com/file/d/0B3XVjcsci0y3VDBTc01PYkhOckE/view?usp=sharing
ggplot(PM, aes(UTM.X, UTM.Y)) + geom_tile(aes(fill = Value), alpha = 0.8, color = "black") +
scale_fill_gradient(low = 'green', high = 'red')