[英]using ggmap to plot points randomly distributed within boundaries of shape file
Is it possible to use ggplot2 / ggmap to plot geom_points randomly within a given spatial area defined by a shapefile? 是否可以使用ggplot2 / ggmap在shapefile定义的给定空间区域内随机绘制geom_points?
I considered geom_jitter, however I need the plots to be randomly distributed and not cross spatial borders. 我考虑了geom_jitter,但是我需要将图随机分布并且不跨越空间边界。
Sample data shamelessly borrowed from @matthiash here . 从@matthiash无耻借用的样本数据在这里 。
library(rgdal)
library(ggmap)
# Get shapefile with Drammen municipality borders
tmpzip<-tempfile()
tmpdir<-tempfile()
dir.create(tmpdir)
download.file("http://www.kartverket.no/Documents/Kart/N50-N5000%20Kartdata/33_N5000_shape.zip",tmpzip)
unzip(tmpzip, exdir=tmpdir)
kommune <- readOGR(dsn=tmpdir, layer="NO_AdminOmrader_pol")
kommune<-kommune[kommune$NAVN=="Drammen",]
kommune<-spTransform(kommune, CRS("+init=epsg:4326"))
dat<-fortify(kommune)
#get the base map
map <- get_map(location = "Drammen",
maptype = "watercolor", source = "stamen", zoom = 11)
Below code plots the base map with region id 154 from the shapefile plotted on top. 下面的代码从顶部绘制的shapefile中绘制了ID为154的底图。
ggmap(map, extent = "normal", maprange = TRUE)+
geom_polygon(data = dat,
aes(long, lat, group = group),
fill = "orange", colour = "red", alpha = 0.2)
What I'd like to do is plot 10 points randomly within the shapefile region defined by dat$id==154 我想做的是在dat $ id == 154定义的shapefile区域内随机绘制10个点
Ok, I sorted it out. 好的,我整理了一下。 The solution is in spsample() in package "raster".
解决方案在软件包“ raster”中的spsample()中。
d<-data.frame(id=NA,x=NA,y=NA)
l<-data.frame(id=154,n=10)
for (i in unique(l$id)){
temp<-spsample(kommune[which(kommune$OBJECTID==i),],n=l[l$id==i,"n"],type="random")
temp<-as.data.frame(temp)
temp$id<-i
d<-rbind(d,temp[,c("id","x","y")])
}
d<-d[-1,] #drop the first empty row
ggmap(map, extent = "normal", maprange = T)+
geom_polygon(data = dat,
aes(long, lat, group = group),
fill = "blue", colour = "yellow", alpha = 0.1)+
geom_point(aes(x = x, y = y), data = d[which(d$id==154),], alpha = .9,show.legend = T)
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