Question

使用ggplot2创建choropleth。这是ggplot代码

okc <- ggplot() +
  geom_polygon(data = mapdata, aes(x = long, y = lat, group = group,
                                   fill = B19013_001), color = "black", size = 0.5)+
  scale_fill_distiller(palette = "Reds", labels = comma,
                       breaks = pretty_breaks(n = 10), values = c(1,0)) +
  guides(fill = guide_legend(reverse = TRUE)) +
  theme_nothing(legend = TRUE) +
  ggtitle('Map of 40109')

这是来自mapdata的数据样本：

       long      lat order  hole piece         group          id
1 -97.54285 35.51951     1 FALSE     1 40109100100.1 40109100100
2 -97.54282 35.51954     2 FALSE     1 40109100100.1 40109100100
3 -97.54280 35.51963     3 FALSE     1 40109100100.1 40109100100
4 -97.54276 35.51976     4 FALSE     1 40109100100.1 40109100100
5 -97.54270 35.51993     5 FALSE     1 40109100100.1 40109100100
6 -97.54266 35.52016     6 FALSE     1 40109100100.1 40109100100
                                          NAME state county  tract B19013_001
1 Census Tract 1001, Oklahoma County, Oklahoma    40    109 100100      33440
2 Census Tract 1001, Oklahoma County, Oklahoma    40    109 100100      33440
3 Census Tract 1001, Oklahoma County, Oklahoma    40    109 100100      33440
4 Census Tract 1001, Oklahoma County, Oklahoma    40    109 100100      33440
5 Census Tract 1001, Oklahoma County, Oklahoma    40    109 100100      33440
6 Census Tract 1001, Oklahoma County, Oklahoma    40    109 100100      33440

它产生了这个情节。

我还使用ggmap创建了一个道路地图。这是代码：

map <- get_map(location = c(lon = mean(mapdata$lon), lat = mean(mapdata$lat))
               , zoom = 10
               , maptype = "roadmap"
               , color = "bw")
p <- ggmap(map) +
  scale_x_continuous(limits = c(min(mapdata$lon), max(mapdata$lon)), expand = c(0, 0)) +
  scale_y_continuous(limits = c(min(mapdata$lat), max(mapdata$lat)), expand = c(0, 0))
p

这是它产生的地图。

当我尝试将它们组合起来时，虽然我收到错误。这是我用来组合它们和错误的代码：

okc <- okc + p

Error in p + o : non-numeric argument to binary operator
In addition: Warning message:
Incompatible methods ("+.gg", "Ops.data.frame") for "+"

我不确定为什么我会收到此错误。是因为地图的缩放比例不一样吗？除了使用非常不精确的缩放功能之外，我无法想象如何缩放ggmap。如果有人对如何在ggmap上叠加等值区有任何想法，我将非常感激。

这里是剩下的代码，用于重新创建ggplot等值线。

    library(acs)
    library(ggplot2)
    library(ggmap)
    library(UScensus2010)
    library(RColorBrewer)
    library(dplyr)
    library(scales)

    #http://api.census.gov/data/key_signup.html
    api.key.install(key="c369cd6ed053a84332caa62301eb8afe98bed825")

    # Load in Shape File (You'll need to download this file from the census)
    #ftp://ftp2.census.gov/geo/tiger/TIGER2013/TRACT/tl_2013_40_tract.zip

    ## load, subset shapefile
    geodat<-readShapePoly("insert shapefile here", proj4string=CRS('+proj=longlat +datum=NAD83'))
    geodat<-geodat[geodat$COUNTYFP==109,]

    ## fortify for ggplot digestion
    geodat.f<-fortify(geodat,region="GEOID")

    # American Community Survey Data: Median HH Income for OK Census Tracts
    ok.counties=geo.make(state="OK", county="Oklahoma", tract="*")
    ok.income<-acs.fetch(geography=ok.counties, table.number="B19013", endyear=2013)


    # Merge Data Sets 
    geo_dat<-geography(ok.income)
    var_dat<-as.data.frame(estimate(ok.income))
    acs_data<-cbind(geo_dat,var_dat)
    acs_data$id<- paste("40109", acs_data$tract, sep = "")

    ## from dplyr
    mapdata<-left_join(geodat.f,acs_data)

    okc <- ggplot() +
      geom_polygon(data = mapdata, aes(x = long, y = lat, group = group,
                                       fill = B19013_001), color = "black", size = 0.5)+
      scale_fill_distiller(palette = "Reds", labels = comma,
                           breaks = pretty_breaks(n = 10), values = c(1,0)) +
      guides(fill = guide_legend(reverse = TRUE)) +
      theme_nothing(legend = TRUE) +
      ggtitle('Map of OKC')

Answer 1

这实际上在Leaflet中做得更好。它看起来更美观，代码也更直观。

library(leaflet)
library(rgdal)
library(RColorBrewer)

pal <- colorNumeric("OrRd", domain = new$pct_minority_popn)

leaflet(mapdata) %>%
 addTiles %>%
 addPolygons(stroke=T, fillOpacity=.5, smoothFactor=.5, color=~pal(B19013_001)) %>%
 addLegend("bottomright", pal=pal, values=~B19013_001, title="Legend Title", opacity=.8)

您可以通过将addTiles命令替换为addProviderTiles（＆＃34; CartoDB.Positron＆＃34;）来更改底部地图。您可以在https://rstudio.github.io/leaflet/basemaps.html

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结合ggplot和ggmap

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