使用 ggmap 的世界地图 [英] World map with ggmap

问题描述

我正在使用 ggmap 并希望有一张以澳大利亚为中心的世界地图，我可以轻松地绘制地理编码点.与其他一些映射包相比，ggmap 似乎更容易使用.然而，当我使用下面的代码查看地图时，它会出错.

I am using ggmap and wish to have a map of the world centered on Australia to which I can easily plot geocoded points. ggmap seems to be a lot easier to use compared to some of the other mapping packages. Yet when I bring through a map using the code below it errors.

gc <- geocode('australia')
center <- as.numeric(gc) 
> map <- get_map(location = center, source="google", maptype="terrain", zoom=0)
Error: zoom must be a whole number between 1 and 21

来自 get_map 帮助:"zoom: 地图缩放，一个从0(整个世界)到21(建筑物)的整数，默认值10(城市).openstreetmaps限制了18的缩放，雄蕊图的限制取决于maptype.'auto' 自动确定边界框规格的缩放比例，默认为 10，具有中心/缩放规格."

From the get_map help: "zoom: map zoom, an integer from 0 (whole world) to 21 (building), default value 10 (city). openstreetmaps limits a zoom of 18, and the limit on stamen maps depends on the maptype. 'auto' automatically determines the zoom for bounding box specifications, and is defaulted to 10 with center/zoom specifications."

将缩放更改为 1 不会导致 get_map 出错，但会导致绘制该地图

Changing the zoom to one does not error for get_map but does for plotting that map

map <- get_map(location = center, source="google", maptype="terrain", zoom=1)
ggmap(map)

Warning messages:
1: In min(x) : no non-missing arguments to min; returning Inf
2: In max(x) : no non-missing arguments to max; returning -Inf
3: In min(x) : no non-missing arguments to min; returning Inf
4: In max(x) : no non-missing arguments to max; returning -Inf

看起来经度没有被拉过.最后，缩放为 2 它确实可以工作，但不会带来整个世界的地图

It looks like the longitude isn't being pulled through. Finally with a zoom of 2 it does work but does not bring through a map of the whole world

那么，我的问题是如何使用 get_map 来获取世界地图?

So, my question is how can I use get_map to get a world map?

会话信息:

会话信息()R 版本 2.15.0 (2012-03-30)平台:i386-pc-mingw32/i386(32位)

sessionInfo() R version 2.15.0 (2012-03-30) Platform: i386-pc-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=English_United Kingdom.1252 
[2] LC_CTYPE=English_United Kingdom.1252   
[3] LC_MONETARY=English_United Kingdom.1252
[4] LC_NUMERIC=C                           
[5] LC_TIME=English_United Kingdom.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] mapproj_1.1-8.3 maps_2.2-6      rgdal_0.7-12    sp_0.9-99      
[5] ggmap_2.1       ggplot2_0.9.1  

loaded via a namespace (and not attached):
[1] colorspace_1.1-1   dichromat_1.2-4    digest_0.5.2       grid_2.15.0       
[5] labeling_0.1       lattice_0.20-6     MASS_7.3-17        memoise_0.1       
[9] munsell_0.3        plyr_1.7.1         png_0.1-4          proto_0.3-9.2     
[13] RColorBrewer_1.0-5 reshape2_1.2.1     RgoogleMaps_1.2.0  rjson_0.2.8       
[17] scales_0.2.1       stringr_0.6        tools_2.15.0 

推荐答案

EDIT:更新到 ggplot2 v 0.9.3

EDIT: Updated to ggplot2 v 0.9.3

我最近尝试了类似的东西，但收效甚微.但是，有多种方法可以将 map 包中的世界地图居中:参见 此处，此处 和 此处.使用后者的代码，这里有一个示例，该示例将世界地图以经度 160 为中心，在使用 ggplot2 绘制的世界地图上绘制 CRAN 镜像位置(使用 ggmap 包中的 geocode() 函数获得的坐标), 和颜色新西兰(使用 geom_polygon).将地图以经度 160 度为中心，将整个非洲置于地图左侧，将格陵兰岛的大部分地区置于地图右侧.

I tried something similar recenty but with little success. However, there are a number of ways to centre a world map from the map package: see here, here, and here. Using code from the latter, here's an example that centers the world map on longitude 160, plots CRAN mirror locations (coordinates obtained using the geocode() function from the ggmap package) on the world map plotted using ggplot2, and colours New Zealand (using geom_polygon). Centering the map on longitude 160 keep all of Africa on the left of the map, and most of Greenland on the right of the map.

library(maps)
library(plyr)
library(ggplot2)
library(sp)
library(ggmap)

# Get some points to plot - CRAN Mirrors
Mirrors = getCRANmirrors(all = FALSE, local.only = FALSE)

Mirrors$Place = paste(Mirrors$City, ", ", Mirrors$Country, sep = "")    # Be patient
tmp = geocode(Mirrors$Place)
Mirrors = cbind(Mirrors, tmp)

###################################################################################################
# Recentre worldmap (and Mirrors coordinates) on longitude 160
### Code by Claudia Engel  March 19, 2012, www.stanford.edu/~cengel/blog

### Recenter ####
center <- 160 # positive values only

# shift coordinates to recenter CRAN Mirrors
Mirrors$long.recenter <- ifelse(Mirrors$lon < center - 180 , Mirrors$lon + 360, Mirrors$lon)

# shift coordinates to recenter worldmap
worldmap <- map_data ("world")
worldmap$long.recenter <- ifelse(worldmap$long < center - 180 , worldmap$long + 360, worldmap$long)

### Function to regroup split lines and polygons
# Takes dataframe, column with long and unique group variable, returns df with added column named group.regroup
RegroupElements <- function(df, longcol, idcol){
  g <- rep(1, length(df[,longcol]))
  if (diff(range(df[,longcol])) > 300) { # check if longitude within group differs more than 300 deg, ie if element was split
    d <- df[,longcol] > mean(range(df[,longcol])) # we use the mean to help us separate the extreme values
    g[!d] <- 1 # some marker for parts that stay in place (we cheat here a little, as we do not take into account concave polygons)
    g[d] <- 2 # parts that are moved
  }
  g <- paste(df[, idcol], g, sep=".") # attach to id to create unique group variable for the dataset
  df$group.regroup <- g
  df
}

### Function to close regrouped polygons
# Takes dataframe, checks if 1st and last longitude value are the same, if not, inserts first as last and reassigns order variable
ClosePolygons <- function(df, longcol, ordercol){
  if (df[1,longcol] != df[nrow(df),longcol]) {
    tmp <- df[1,]
    df <- rbind(df,tmp)
  }
  o <- c(1: nrow(df)) # rassign the order variable
  df[,ordercol] <- o
  df
}

# now regroup
worldmap.rg <- ddply(worldmap, .(group), RegroupElements, "long.recenter", "group")

# close polys
worldmap.cp <- ddply(worldmap.rg, .(group.regroup), ClosePolygons, "long.recenter", "order") # use the new grouping var
#############################################################################

# Plot worldmap using data from worldmap.cp
windows(9.2, 4)
worldmap = ggplot(aes(x = long.recenter, y = lat), data = worldmap.cp) + 
  geom_polygon(aes(group = group.regroup), fill="#f9f9f9", colour = "grey65") + 
  scale_y_continuous(limits = c(-60, 85)) + 
  coord_equal() +  theme_bw() + 
  theme(legend.position = "none",
    panel.grid.major = element_blank(),
    panel.grid.minor = element_blank(),
    axis.title.x = element_blank(),
    axis.title.y = element_blank(),
    #axis.text.x = element_blank(),
    axis.text.y = element_blank(),
    axis.ticks = element_blank(), 
    panel.border = element_rect(colour = "black"))

# Plot the CRAN Mirrors
worldmap = worldmap + geom_point(data = Mirrors, aes(long.recenter, lat),
   colour = "red", pch = 19, size = 3, alpha = .4)

# Colour New Zealand
# Take care of variable names in worldmap.cp
head(worldmap.cp)
worldmap + geom_polygon(data = subset(worldmap.cp, region == "New Zealand", select = c(long.recenter, lat, group.regroup)), 
          aes(x = long.recenter, y = lat, group = group.regroup), fill = "blue")

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