使用sf对象自定义ggplot2中的图例

Question

我正在用sf绘制（映射）ggplot2对象。我的理解是，自版本2.2.1 ggplot2以来，地理元素geom_sf用于简单要素对象。

我可以通过执行以下操作来生成所需的确切地图：

library(sf)
library(ggplot2)

# some points to start with
a <- st_as_sf(data.frame(lon = c(1,4,6), lat = c(0,0,-3)), coords = c('lon', 'lat'))
b <- st_as_sf(data.frame(lon = c(2.5,4), lat = c(-4.5,-5)), coords = c('lon', 'lat'))

# circles around those points
buf.a <- st_buffer(a, 1)
buf.b <- st_buffer(b, 1)

# colors to mark the points
sol.a = rgb(1,0,0) 
sol.b = rgb(0,0,1) 

# colors to fill the circles
fil.a = adjustcolor(sol.a, alpha.f = .25)
fil.b = adjustcolor(sol.b, alpha.f = .25)

# the plot I want
g = ggplot() +
    geom_sf(data = buf.a, fill =  fil.a, color = NA) +
    geom_sf(data = buf.b, fill =  fil.b, color = NA) +
    geom_sf(data = a,     color = sol.a, shape = 20, size = 3) +
    geom_sf(data = b,     color = sol.b, shape = 20, size = 3)
g

产生

这是我想要的，除了它缺少图例。为此，我正在做

cols.fill = c("GROUP A" = fil.a, "GROUP B" = fil.b)
cols.sol = c("GROUP A" = sol.a, "GROUP B" = sol.b)

g = ggplot() +
    geom_sf(data = buf.a, color = NA, aes(fill = 'GROUP A')) +
    geom_sf(data = buf.b, color = NA, aes(fill = 'GROUP B')) +
    geom_sf(data = a,     shape = 20, size = 3, aes(color = 'GROUP A')) + 
    geom_sf(data = b,     shape = 20, size = 3, aes(color = 'GROUP B')) +
    scale_fill_manual(name = "circles", values = cols.fill) +
    scale_color_manual(name = "points", values = cols.sol)
g

给出

那不是我想要的，因为在传说中：

1. “点”应该是点（不是正方形）；和
2. “圆圈”应该是圆圈（同样，不是正方形）

如果图例可以尊重我的颜色的透明度（在此示例中如此），那就太好了。

我试图将上述内容的最后几行更改为

scale_fill_manual(name = "circles", values = cols.fill,
                  guide = guide_legend(override.aes = list(shape = c(19, 19)))) +
scale_color_manual(name = "points", values = cols.sol,
                   guide = guide_legend(override.aes = list(shape = c(20, 20))))

但这对我的情节没有任何作用。

想法？

注意：如果最终对于绘图来说更简单，则可以更改数据的结构，例如，通过在同一简单要素对象中合并对象a和b并添加一列指示组（与buf.a和buf.b相同）。

Answer 1

这是我设法到达的距离。

g = ggplot() +
    geom_sf(data = buf.a, color = NA, aes(fill = 'GROUP A'), show.legend = "point") +
    geom_sf(data = buf.b, color = NA, aes(fill = 'GROUP B'), show.legend = "point") +
    geom_sf(data = a,     shape = 20, size = 3, aes(color = 'GROUP A'), show.legend = "point") + 
    geom_sf(data = b,     shape = 20, size = 3, aes(color = 'GROUP B'), show.legend = "point") +
    scale_color_manual(name = "points", values = cols.sol,
                       guide = guide_legend(override.aes = list(shape = c(20, 20)))) +
    scale_fill_manual(name = "circles", values = cols.fill,
                      guide = guide_legend(override.aes = list(shape = c(20, 20), color = cols.fill, size = 8)))
g

要摆脱图例符号中的灰色背景，

g + theme(legend.key = element_rect(fill = "white"))

这里唯一的问题是圈子没有我想要的透明度。这很奇怪。

Answer 2

要获得图例中的透明度，需要将其添加到override.aes中，请尝试：

guide = guide_legend(override.aes = list(alpha = 0.5, shape = c(20, 20), color = cols.fill, size = 8, )))