添加geom_point时ggplot地图会发生变化

如何解决添加geom_point时ggplot地图会发生变化

我正在尝试使用 ggplot 并在我的纬度/经度点中进行分层来创建地图。

我毫无问题地创建了美国地图，但是当我在 geom_point lat/lon 位置分层时，美国地图会缩小并发生变化。有人可以指出我为什么会这样吗？

stateData <- map_data('state')
head(stateData)
us <- fortify(stateData,region = 'region')
gg <- ggplot() + geom_map(data  =  us,map = us,aes(x = long,y = lat,map_id = region,group = group),fill = 'white',color = 'black',size = 0.25) + 
  coord_map('albers',lat0 = 39,lat1 = 45) +
  theme_map()


gg + #add the data points with lon/lat declaring the columns
  geom_point(data=new_datav2,aes(x=lon,y=lat),color='red',alpha=0.15)

postalCode  county                 lat       lon
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94612   Alameda County  37.80508041 -122.2730713
94002   San Mateo County    37.51834106 -122.276207
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94612   Alameda County  37.80508041 -122.2730713
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94102   San Francisco County    37.77711868 -122.4196396
94063   San Mateo County    37.48450089 -122.2277222
94102   San Francisco County    37.77711868 -122.4196396
94596   Contra Costa County 37.90118027 -122.0616226
94102   San Francisco County    37.77711868 -122.4196396
94704   Alameda County  37.86988068 -122.2705383
94612   Alameda County  37.80508041 -122.2730713

解决方法

通过查看您的图像，很明显您有一个位于美国东北部的红点。您提供的示例集中没有这一点。我将模拟一个类似的异常值，但代码应该可以解决投影问题。

点集：

df_points <- 
structure(list(
    postalCode = c(94102,94612,94102,94063,0),County = c("San Francisco County","Alameda County","San Francisco County","San Mateo County","This_is_the_outlier"),lat = c(37.77711868,37.80508041,37.77711868,37.48450089,40),lon = c(-122.4196396,-122.2730713,-122.4196396,-122.2277222,-10)),row.names = c(NA,-5L),class = c("tbl_df","tbl","data.frame"))

映射道具：

library(tidyverse)
library(maps)
library(mapproj)
library(ggthemes)

us <- fortify(stateData,region = 'region')
gg <- ggplot() + 
  geom_map(data  =  us,map = us,aes(x = long,y = lat,map_id = region,group = group),fill = 'white',color = 'black',size = 0.25) +
  coord_map('albers',lat0 = 39,lat1 = 45) +
  theme_map()

第一个选择，过滤异常值。

gg + #add the data points with lon/lat declaring the columns
  geom_point(data=df_points %>% filter(lon < -65),## Here is where you filer the eastern outlier by excluding all data east of longitude 65W.
             aes(x=lon,y=lat),color='red',alpha=0.15)

第二种选择，限制绘图的水平范围。

gg + #add the data points with lon/lat declaring the columns
  geom_point(data=df_points,aes(x=lon,alpha=0.15) +
    coord_map(xlim = c(-130,-65)) # Here you crop the plotting images from 130W to 65W.