格式化多个geom_sf图例

Question

我正在 ggplot 中处理多个 sf 几何形状，并希望以点、线和正方形（用于多边形）的形式显示图例。但是，geom_sf图例结合了如下所示的几何特征（即组合线和点）：

library(ggplot2)
library(sf)

poly1 <- cbind(lon = c(5, 6, 7, 5), lat = c(52, 53, 51, 52))

poly <- st_sf(st_sfc(st_polygon(list(poly1))))
line <- st_sf(st_sfc(list(st_linestring(cbind(lon = c(5.5, 4.5), lat = c(53.5, 54.5))))))
point <- st_sf(st_sfc(st_point(cbind(lon = 5.5, lat = 52.7))))

ggplot() +
  geom_sf(data = poly, aes(fill = "A")) +
  geom_sf(data = point, aes(colour = "B"), show.legend = "point") +
  geom_sf(data = line, aes(colour = "C"), show.legend = "line") +
  scale_fill_manual(values = c("A" = "yellow")) +
  scale_colour_manual(values = c("B" = "pink", "C" = "purple")) +
  theme_minimal()

我想要三个单独的图例，一个黄色的正方形，一个粉色的点，和一条紫色的线。这只是我绘制单个几何图形时的情况，而不是三个几何图形的组合。

我查找了类似的主题，但没有一个涉及点几何，即 https://github.com/tidyverse/ggplot2/issues/2460

有人能对此提供任何见解吗？

GitHub问题：https://github.com/tidyverse/ggplot2/issues/2763

Answer 1

我知道如何分离图例，它们现在只能组合起来，因为您要映射两次颜色。通过将形状映射到点并设置颜色，可以解决以下问题：

ggplot() +
  geom_sf(data = poly, aes(fill = "A")) +
  geom_sf(data = point, aes(colour = "B"), show.legend = "point") +
  geom_sf(data = line, aes(shape = "C"), show.legend = "line", color = 'purple') +
  scale_fill_manual(name = NULL, values = c("A" = "yellow")) +
  scale_colour_manual(name = NULL, values = c("B" = "pink")) +
  scale_shape_discrete(
    name = NULL, 
    guide = guide_legend(override.aes = list(color = 'purple'))) +
  theme_minimal()

但是:点和线仍然出现在所有三个图例中。我觉得他们不应该！也许你可以填补一个github问题。

Answer 2

受@Axeman的评论、这个问题和这篇文章的启发，使用guide_legend（）中的override.aes参数解决了这个问题：

library(ggplot2)
library(sf)

poly1 <- cbind(lon = c(5, 6, 7, 5), lat = c(52, 53, 51, 52))

poly <- st_sf(st_sfc(st_polygon(list(poly1))))
line <- st_sf(st_sfc(list(st_linestring(cbind(lon = c(5.5, 4.5), lat = c(53.5, 54.5))))))
point <- st_sf(st_sfc(st_point(cbind(lon = 5.5, lat = 52.7))))

ggplot() +
  geom_sf(data = poly, aes(fill = "A")) +
  geom_sf(data = point, aes(colour = "B"), show.legend = "point") +
  geom_sf(data = line, aes(colour = "C"), show.legend = "line") +
  scale_fill_manual(values = c("A" = "yellow"), name = NULL,
                    guide = guide_legend(override.aes = list(linetype = "blank", shape = NA))) +
  scale_colour_manual(values = c("B" = "pink", "C" = "purple"), name = NULL,
                      guide = guide_legend(override.aes = list(linetype = c("blank", "solid"), 
                                                               shape = c(16, NA)))) +
  theme_minimal()