3
内绘制的再生用,请考虑以下数据:GGPLOT2/GIS多边形区域
library(rgdal)
library(ggplot2)
library(rgeos)
download.file("http://spatialanalysis.co.uk/wp-content/uploads/2010/09/London_Sport.zip",
destfile = "London_Sport.zip")
unzip("London_Sport.zip")
projection="+proj=merc"
london_shape = readOGR("./", layer="london_sport")
# Create random points
set.seed(1)
points = data.frame(long=rnorm(10000, mean=-0.1, sd=0.1), lat=rnorm(10000, mean=51.5, sd=0.1))
points = SpatialPoints(points, proj4string=CRS("+proj=latlon"))
# Transform data to our projection
london = spTransform(london_shape, CRS(projection))
points = spTransform(points, CRS(projection))
# Keeps only points inside London
intersection = gIntersects(points, london, byid = T)
outside = apply(intersection == FALSE, MARGIN = 2, all)
points = points[which(!outside), ]
# Blank theme
new_theme_empty <- theme_bw()
new_theme_empty$line <- element_blank()
new_theme_empty$rect <- element_blank()
new_theme_empty$strip.text <- element_blank()
new_theme_empty$axis.text <- element_blank()
new_theme_empty$plot.title <- element_blank()
new_theme_empty$axis.title <- element_blank()
new_theme_empty$plot.margin <- structure(c(0, 0, -1, -1), unit = "lines", valid.unit = 3L, class = "unit")
# Prepare data to ggplot
london = fortify(london)
points = as.data.frame(points)
我想积点的密度图。我可以通过使用stat_bin2d
这样做:
ggplot() +
geom_polygon(data=london, aes(x=long,y=lat,group=group), fill="black") +
stat_bin2d(data=points, aes(x=long,y=lat), bins=40) +
geom_path(data=london, aes(x=long,y=lat,group=id), colour='white') +
coord_equal() +
new_theme_empty
但是,这导致密度广场的某些部分可以被绘制伦敦之外:
我怎么能只绘制密度图在伦敦?
如果你要绘制的东西已经是多边形内,你可以设置线的*色*为多边形为白色,按原样绘制。如果不是这种情况,请参阅[rgeos软件包]中的'gDifference'函数(http://cran.r-project.org/web/packages/rgeos/index.html)。与往常一样,如果您提供了一个可重复使用的小例子,那么您可以帮助其他人。 –
只是放了一个可重复的例子:) –
这个链接可能会有所帮助:http://spatial.ly/2013/12/introduction-spatial-data-ggplot2/ – tonytonov