根据人口数量着色ggplot地图

Question

我有一个包含超过50,000个数据的数据集。该数据集包括对象，经度和纬度（具有以下结构）。

coord <- data.frame(object = c("a","b","c","d","e","f","h","i","j","k"), LON = c(-73.95 ,-73.97,-73.95,-73.91,-73.91,-73.93,-73.96, -73.90,-73.97,-73.94),LAT =c(40.60,40.68,40.68,40.85,40.83,40.72,40.65, 40.74, 40.69, 40.82)) 

我打算着色不同地区的地图。我找到了下面的示例代码。

library(rgeos) 
library(maptools) 
library(geojsonio) 
library(ggplot2) 
URL <- "http://services5.arcgis.com/GfwWNkhOj9bNBqoJ/arcgis/rest/services/nycd/FeatureServer/0/query?where=1=1&outFields=*&outSR=4326&f=geojson" 
fil <- "nyc_community_districts.geojson" 
if (!file.exists(fil)) download.file(URL, fil) 
nyc_districts <- geojson_read(fil, what="sp") 
nyc_districts_map <- fortify(nyc_districts, region="BoroCD") 
mids <- cbind.data.frame(as.data.frame(gCentroid(nyc_districts, byid=TRUE)),id=nyc_districts$BoroCD) 
gg <- ggplot() 
gg <- gg + geom_map(data=nyc_districts_map, map=nyc_districts_map, 
       aes(x=long, y=lat, map_id=id), 
       color="#2b2b2b", size=0.15, fill=NA) 
gg <- gg + geom_text(data=mids, aes(x=x, y=y, label=id), size=2) 
gg <- gg + coord_map() 
gg <- gg + ggthemes::theme_map() 

然后，我用这个代码着色不同地区

library(viridis) 
# make up some fill data 
set.seed(1492) 
df <- data.frame(LON = c(-73.95770,-73.95445,-73.96215,-73.97739,-73.98136,-73.93974,-73.95061, -73.98609 ,-73.95724,-73.93351,-73.94931),LAT =c(40.81099,40.71415,40.71025,40.68983,40.66715,40.79821,40.66830, 40.68980, 40.71636, 40.76621, 40.80273)) 

pointsSp <- SpatialPoints(coords = df[,c("LON", "LAT")], 
         proj4string = CRS(proj4string(nyc_districts))) 
nyc_districts$pointCount <- 0 
for(i in 1:length(nyc_districts)){ 
    x <- nyc_districts[i,] 
    nyc_districts$pointCount[i] <- length(x[pointsSp,]) 
} 

choro <- data.frame(district=nyc_districts@data$BoroCD, 
       fill=sample(100, nrow(nyc_districts@data))) 
gg <- ggplot() 
gg <- gg + geom_map(data=nyc_districts_map, map=nyc_districts_map, 
       aes(x=long, y=lat, map_id=id), 
       color="#2b2b2b", size=0.15, fill=NA) 
gg <- gg + geom_map(data=choro, map=nyc_districts_map, 
       aes(fill=fill, map_id=district), 
       color="#2b2b2b", size=0.15) 
gg <- gg + geom_point(data=coord, aes(x=LON, y=LAT), 
        colour= "red", alpha=1,na.rm=T) 
gg <- gg + scale_fill_viridis(name="Pick ups\ndistribution") +  geom_text(data=mids, aes(x=x, y=y, label=id), size=2) 
gg <- gg + coord_map() 
gg <- gg + ggthemes::theme_map() 
gg <- gg + theme(legend.position=c(0.1,0.5)) 
gg 

在上面的代码中，有GEOM点我可以在地图上显示不同的协调的位置。但是我的区域着色是错误的。你能告诉我如何根据“坐标”数据集对地图着色。

Answer 1

您必须执行与每个多边形相交的点数的“空间连接”。因此，这些点必须转换为SpatialPoints对象。

pointsSp <- SpatialPoints(coords = coord[,c("LON", "LAT")], 
          proj4string = CRS(proj4string(nyc_districts))) 

之后，我们采取了nyc_districts的每个多边形，并计算在每个点的数目。

nyc_districts$pointCount <- 0 
for(i in 1:length(nyc_districts)){ 
    x <- nyc_districts[i,] 
    nyc_districts$pointCount[i] <- length(pointsSp[x,]) 
} 

然后你只需要改变的代码的脉络膜线以下，基本上改变了sample(...)（这是有用于测试目的...）我们上面创建的变量。之后，您创建的情节就像你在问：

choro <- data.frame(district=nyc_districts@data$BoroCD, 
        fill=nyc_districts$pointCount) 

结果看起来是这样做的：