在SpatialPolygonsR外部绘制标签

问题描述

我正在尝试向Spatialpolygons添加标签，这些标签将在多边形外部绘制。我正在使用R和基本绘图功能来堆叠地图的图层。

这是带有来自polygonsLabel（）函数的标签的多边形的示例。（https://www.rdocumentation.org/packages/rgeos/versions/0.3-5/topics/polygonsLabel）

#Create polygons 
x1 = c(0,4,0)
y1 = c(0,0)
x2 = c(1,1,3,1)
y2 = c(-2,-10,-2,-2)
x3 = c(6,14,6,6)
y3 = c(1,1)
xy.sp = Spatialpolygons(list(
  polygons(list(polygon(cbind(x1,y1))),ID = "test1"),# Box
  polygons(list(polygon(cbind(x3,y3))),ID = "test3"),# wide
  polygons(list(polygon(cbind(x2,y2))),ID = "test2")  # high
))

#Plot polygons
plot(xy.sp,col=terrain.colors(3))

#Add labels:
labels=c("Hi!","A very long text string","N
a
r
r
o
w")

polygonsLabel(xy.sp,labels,cex=.8,col = c('white','black','maroon'))

解决方法

使用sf和ggsflabel软件包应该可以为您提供所需的东西。

下面，我将您的sp对象更改为sf（简单功能）对象，然后添加了标签文本列。

ggsflabel软件包信息可在以下位置找到：https://yutannihilation.github.io/ggsflabel/index.html

您可能需要调整绘图的推力和力度。

library(rgeos)
#> Loading required package: sp
#> rgeos version: 0.5-3,(SVN revision 634)
#>  GEOS runtime version: 3.8.0-CAPI-1.13.1 
#>  Linking to sp version: 1.4-2 
#>  Polygon checking: TRUE
library(sf)
#> Linking to GEOS 3.8.0,GDAL 3.0.4,PROJ 6.3.1
library(tidyverse)
library(sp)
library(ggsflabel)
#> 
#> Attaching package: 'ggsflabel'
#> The following objects are masked from 'package:ggplot2':
#> 
#>     geom_sf_label,geom_sf_text,StatSfCoordinates

x1 = c(0,4,0)
y1 = c(0,0)
x2 = c(1,1,3,1)
y2 = c(-2,-10,-2,-2)
x3 = c(6,14,6,6)
y3 = c(1,1)
xy.sp = SpatialPolygons(list(
  Polygons(list(Polygon(cbind(x1,y1))),ID = "test1"),# box
  Polygons(list(Polygon(cbind(x3,y3))),ID = "test3"),# wide
  Polygons(list(Polygon(cbind(x2,y2))),ID = "test2")  # high
))

rm(x1,y1,x2,y2,x3,y3)

#Plot polygons
plot(xy.sp,col=terrain.colors(3))

#Add labels:
labels=c("Hi!","A very long text string","N
a
r
r
o
w")

polygonsLabel(xy.sp,labels,cex=.8,col = c('white','black','maroon'))

#>          [,1]      [,2]
#> [1,] 2.001002  1.966994
#> [2,] 9.828784  2.000169
#> [3,] 1.999282 -6.597297


# Change sp object to sf,and add a label column
xy_sf <- st_as_sf(xy.sp)
xy_sf$labels <- labels

ggplot(xy_sf) + 
  geom_sf(fill = c('white','maroon')) + 
  geom_sf_label_repel(aes(label = labels),nudge_y = -3,nudge_x = +2,force = 100)

^{由reprex package（v0.3.0）于2020-10-01创建}

*编辑：

从边缘标记线：

ggplot(xy_sf) + 
  geom_sf_label_repel(aes(label = labels),force = 100) +
  geom_sf(fill = c('white','maroon'))

gis label label label label polygon r r