R：如何使用ggplot向地图添加刻度和标签？

编程问答 2022-06-03

问题描述

我使用ggplot和LAmbert Azimuthal等面积投影（LAEA）映射了一个“ bathy”对象（包“ marmap”）。在此地图上，需要绘制点和路径（按ID分组）的位置。如您所见，所有程序在此阶段都运行良好。但是，我还需要绘制方格图（纬度每20°和长20°）和标签（坐标轴刻度），但是我很难在ggplot中做到这一点。

首先，我加载地图：

library(marmap)
library(ggplot2)
library(dplyr)

# Get data -> raster world map (bathymetry map)
world <- getNOAA.bathy(-180,180,-90,90,resolution = 25,keep = TRUE)

# Switch to raster
world.ras <- as.raster(world)

# Set the projection to LAmbert Azimuthal Equal Area
my.proj <- "+proj=laea +lat_0=40 +lon_0=-30 +x_0=4321000 +y_0=3210000 +ellps=GRS80 +towgs84=0,0 +units=m +no_defs"

world.ras.proj <- projectRaster(world.ras,crs = my.proj)

# Switch back to a bathy object
world.proj <- as.bathy(world.ras.proj)

# fortify raster map
world.proj.df <- fortify(world.proj)

带有位置数据的数据框如下所示：

hmm.stat <- data.frame(lat=c(77.16698,80.26016,59.98226,50.74124,62.19604,65.58466,80.03116,77.31931,51.29168,47.69987),lon=c(12.68404,27.43116,-37.875200,-48.6865620,-30.0061030,3.3246880,43.4332484,19.05524,-35.126510,-43.15675),ID=c(1,1,2,3,3))

coordinates(hmm.stat) <- c("lat","lon") #defined as coordinates
proj4string(hmm.stat) <- CRS("+init=epsg:4326") #defined CRS to WGS 84
hmm.stat.sp <- spTransform(hmm.stat,my.proj) #transform to LAEA
hmm.stat.df <- data.frame(hmm.stat.sp)

以下是使用ggplot映射投影数据的脚本。

map <- ggplot(world.proj.df,aes(x=x,y=y)) +
  geom_raster(aes(fill=z),data=world.proj.df) +
  geom_contour(aes(z=z),breaks=0,#contour for land
               colour="black",size=1) +
  scale_fill_gradientn(values = scales::rescale(c(-5000,3220)),colors = c("steelblue4","#C7E0FF","gray40","white")) +
  coord_cartesian(ylim = c(1900000,9000000),xlim = c(150000,6600000),expand = FALSE) #set map extent

map + geom_path(data = hmm.stat.df,aes(x=lon,y=lat,group = ID),color ='gray10',alpha = 0.5,#transparency
                size = 0.2) +
  geom_point(data = hmm.stat.df,aes(x = lon,y = lat),colour = 'firebrick',size = 1.2,alpha = 0.3,#transparency
             shape = 15) + #dots
  ggtitle("Non-breeding movement") +
        theme(panel.grid.minor.x=element_blank(),#remove grid
        panel.grid.major.x=element_blank(),#remove grid
        panel.grid.minor.y=element_blank(),#remove grid
        panel.grid.major.y=element_blank(),#remove grid
        axis.ticks.x = element_blank(),#remove axes graduation ticks
        axis.ticks.y = element_blank(),#remove axes graduation ticks
        panel.background = element_rect(fill = "white"),axis.text.x = element_blank(),axis.text.y = element_blank(),axis.title.x = element_blank(),axis.title.y = element_blank(),plot.title = element_text(colour = "grey25",size = 45,margin = margin(t = 0,r = 0,b = 12,l = 0)),panel.border = element_rect(colour = 'gray24',fill=NA,size=3),plot.margin = unit(c(0,0),"in"),# plot margins
        legend.position="none") # remove all legends

我希望使用如下创建的刻度：

library(graticule)

#meridians and parallels
lons <- seq(-180,by = 20)
lats <- seq(0,80,by = 20)

#projected graticules
grat <- graticule(lons,lats,proj = my.proj)

#plot graticules
plot(grat,add = TRUE,lty = 5)

当然，ggplot无法直接处理我命名为“ grat”的SpatialLinesDataFrame对象。非常感谢您提供有关如何使用ggplot将这样的刻度（及其标签）添加到以前的地图的帮助。

解决方法

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