仅将地图比例和向北箭头包含在一个ggplot facet中

Question

我正在使用ggplot2和sf包绘制地图,我想使用ggsn包在图中包含地图比例和北向箭头.这是问题所在.我想显示一个有两个或更多的数字,facets但我想将比例和北箭头添加到一个图形面.

有关如何做到这一点的任何想法？

可重复的例子:

library(UScensus2000tract)
library(ggplot2)
library(spdep)
library(sf)
library(ggsn)

# load data
  data("oregon.tract")

# convert spatial object to sf class
  oregon_sf_A <- st_as_sf(oregon.tract)
  oregon_sf_B <- st_as_sf(oregon.tract)

# organize data for facetting
  oregon_sf_A$cat <- "A"
  oregon_sf_B$cat <- "B"
  oregon_sf <- rbind(oregon_sf_A, oregon_sf_B)

# create a second variable for facetting
  oregon_sf$var2 <- sample(c("C","D"), nrow(oregon_sf), replace=T)

# Map
  ggplot() +
    geom_sf(data=oregon_sf, aes(fill=hispanic.t), color=NA) +
    scale_fill_viridis(option = "inferno", direction=-1) +
    facet_grid(~cat) +
    north(data=oregon_sf, symbol=4, location="bottomleft", scale=.2) +
    scalebar(data=oregon_sf, dist = 200, st.size=3, height=0.02, dd2km = TRUE, location="bottomright" , model = 'WGS84')

如果我们尝试使用两个变量,问题会变得复杂一些facet_grid:

# Map 2
  ggplot() +
    geom_sf(data=oregon_sf, aes(fill=hispanic.t), color=NA) +
    scale_fill_viridis(option = "inferno", direction=-1) +
    facet_grid(cat~var2) +
    north(data=oregon_sf, symbol=4, location="bottomleft", scale=.2) +
    scalebar(data=oregon_sf, dist = 200, st.size=3, height=0.02, dd2km = TRUE, location="bottomright" , model = 'WGS84')

Answer 1

使用scalebar中的facet.var和facet.lev参数添加到单个facet。使用north2() 函数添加单个指北针。您可以调整位置/比例等以满足您的需求。如果您将facet_grid与两个变量一起使用，则可以将向量传递给facet.var和facet.lev。

 ggp <- ggplot(data = oregon_sf) +
  geom_sf(aes(fill=hispanic.t), color=NA) +
  scale_fill_viridis(option = "inferno", direction=-1) +
  facet_grid(cat~var2) +
  scalebar(data=oregon_sf, dist = 200, st.size=3, height=0.02, dd2km = TRUE, location="bottomright" , model = 'WGS84',
           facet.var = c('cat', 'var2'), facet.lev = c('B', "C"))
north2(ggp = ggp, scale = 0.1, x = 0.05, y = 0.3, symbol = 4)