r - 如何使用ggmap正确连接数据和几何

一个图像值一千个字:


可观察到的行为:从上图可以看出，国家/地区的名称与它们的实际几何形状不匹配。

预期行为:我想正确地将数据框与其几何形状连接起来，并在ggmap中显示结果。

我以前加入了不同的数据框，但是由于ggmap显然需要“加强”数据框(实际上我并不知道真正的含义)才能显示结果，所以事情变得错误。

这是我到目前为止所做的:

library(rgdal)
library(dplyr)
library(broom)
library(ggmap)

# Load GeoJSON file with countries.
countries = readOGR(dsn = "https://gist.githubusercontent.com/ccamara/fc26d8bb7e777488b446fbaad1e6ea63/raw/a6f69b6c3b4a75b02858e966b9d36c85982cbd32/countries.geojson")

# Load dataframe.
df = read.csv("https://gist.githubusercontent.com/ccamara/fc26d8bb7e777488b446fbaad1e6ea63/raw/a6f69b6c3b4a75b02858e966b9d36c85982cbd32/sample-dataframe.csv")

# Join geometry with dataframe.
countries$iso_a2 = as.factor(countries$iso_a2)
countries@data = left_join(countries@data, df, by = c('iso_a2' = 'country_code'))

# Convert to dataframe so it can be used by ggmap.
countries.t = tidy(countries)

# Here's where the problem starts, as by doing so, data has been lost!

# Recover attributes' table that was destroyed after using broom::tidy.
countries@data$id = rownames(countries@data) # Adding a new id variable.
countries.t = left_join(countries.t, countries@data, by = "id")

ggplot(data = countries.t,
       aes(long, lat, fill = country_name, group = group)) +
  geom_polygon() +
  geom_path(colour="black", lwd=0.05) + # polygon borders
  coord_equal() +
  ggtitle("Data and geometry have been messed!") +
  theme(axis.text = element_blank(), # change the theme options
        axis.title = element_blank(), # remove axis titles
        axis.ticks = element_blank()) # remove axis ticks

最佳答案

行为困惑是有原因的。
countries开始时是一个大型SpatialPolygonsDataFrame，其中包含 177个元素(以及countries@data中的177行)。当您对left_join和countries@data执行df时，countries中的元素数不受影响，但是countries@data中的行数增加到 210 。

使用countries强化broom::tidy会将countries及其177个元素转换为id从0到176的数据帧。(我不确定为什么它的索引从零开始，但是我通常还是更倾向于明确地指定区域)。

另一方面，根据id将countries@data添加到rownames(countries@data)中，会导致id值从1到210，因为这是countries@data较早加入后df中的行数。因此，一切都不同步。

请尝试以下操作:

# (we start out right after loading countries & df)

# no need to join geometry with df first

# convert countries to data frame, specifying the regions explicitly
# (note I'm using the name column rather than the iso_a2 column from countries@data;
# this is because there are some repeat -99 values in iso_a2, and we want
# one-to-one matching.)
countries.t = tidy(countries, region = "name")

# join with the original file's data
countries.t = left_join(countries.t, countries@data, by = c("id" = "name"))

# join with df
countries.t = left_join(countries.t, df, by = c("iso_a2" = "country_code"))

# no change to the plot's code, except for ggtitle
ggplot(data = countries.t,
       aes(long, lat, fill = country_name, group = group)) +
  geom_polygon() +
  geom_path(colour="black", lwd = 0.05) +
  coord_equal() +
  ggtitle("Data and geometry are fine") +
  theme(axis.text = element_blank(),
        axis.title = element_blank(),
        axis.ticks = element_blank())

p.s.您实际上不需要ggmap包。只是它加载的ggplot2软件包。

关于r - 如何使用ggmap正确连接数据和几何，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/46277574/