如何在 spplot 中将比例尺添加到单个面板

Question

我有一组来自 RasterStack 的八张地图，并希望在绘图中添加一个 100 公里的比例尺。我在spplot 函数中使用sp.layout 在栅格顶部添加SpatialLines 对象，并假设比例尺（或指北针）也可以这样做，但我什么也做不了。

我使用的代码是：

library(sp)
library(raster)
library(grid)

spplot(rasterstack, layout=c(2,4),
       names.attr=c("a", "b", "c", "d", "e", "f", "g", "h"),
       between=list(x=1, y=1),
       at=seq(0,1000,by=100),
       col.regions=colorRampPalette(c("grey90","yellow4","green4"))(100),
       par.strip.text=list(cex=2.5),
       scales=list(draw=F),
       colorkey=list(labels=list(labels=seq(0,1,by=0.25),
                                 at=seq(0,1000,by=250),
                                 width=10, cex=2.5)),
       sp.layout=list(list(country, first=FALSE), # add country borders
                      list(spatiallines, lwd=1.5, col=4)))
# Label vertical colorkey
grid::grid.text('Probability of occurrence', y=unit(0.5,"npc"), x=unit(0.95,"npc"), rot=90, gp=gpar(cex=3, font=2))

其中rasterstack是一个8层的RasterStack，每个单元格的取值范围是0到1000，country和spatiallines是SpatialLines*对象

我遇到了各种添加比例尺的功能，例如layout.scale.bar()、maps::map.scale() 和 scalebar()，但我不知道如何将它们合并到我正在使用的 spplot 代码中。我尝试将它们作为参数添加到 spplot 中或作为列表添加到 sp.layout=list() 参数中，但都不起作用。

谢谢！

Answer 1

我推荐layout.scale.bar() 和layout.north.arrow()，因为它们的输出是SpatialPolygons。它们的布局函数名称是"SpatialPolygonsRescale"，您必须将其作为列表的第一个参数。

这是我的例子；

library(sp); library(raster); library(grid)

### example data
r <- raster(system.file("external/test.grd", package="raster"))
range(r)   # 178400, 181600, 329400, 334000  (xmin, xmax, ymin, ymax)
r4 <- stack(r, r, r, r)

### preparation of scalebar etc.
North <- list("SpatialPolygonsRescale", layout.north.arrow(type=1), 
              offset = c(178600, 333000), scale = 800, which = 1)

North2 <- list("SpatialPolygonsRescale", layout.north.arrow(type=2), 
              offset = c(178600, 332000), scale = 1200, fill="gray", which = 2)

scale1 <- list("SpatialPolygonsRescale", layout.scale.bar(), 
               offset = c(180500, 329800), scale = 500, fill=c("transparent","black"), which = 3)
s1_text0 <- list("sp.text", c(180500, 329800 + 150), "0", cex = .5, which = 3)
s1_text1 <- list("sp.text", c(180500 + 500, 329800 + 150), "500 m", cex = .5, which = 3)

scale2.1 <- list("SpatialPolygonsRescale", layout.scale.bar(height=0.1), 
                 offset = c(178600, 333000), scale = 1000, fill=c("red", "green"), which = 4)
s2.1_text0 <- list("sp.text", c(178600, 333000 - 150), "0", cex = .5, which = 4)
s2.1_text1 <- list("sp.text", c(178600 + 1000, 333000 - 150), "1 km", cex = .5, which = 4)

scale2.2 <- list("SpatialPolygonsRescale", layout.scale.bar(), 
                 offset = c(178600, 333200), scale = 2000, fill=c("cyan", "violet"), which = 4)
s2.2_text0 <- list("sp.text", c(178600, 333200 + 300), "0", cex = .5, which = 4)
s2.2_text1 <- list("sp.text", c(178600 + 2000, 333200 + 300), "2000 m", cex = .5, which = 4)
  # Of course, you can write 180600 instead of 178600 + 2000

### draw
spplot(r4, layout=c(2,2),
       sp.layout = list(North, North2, scale1, s1_text0, s1_text1, 
                        scale2.1, s2.1_text0, s2.1_text1, scale2.2, s2.2_text0, s2.2_text1))