如何通过ggplot2中的构面对图例进行分组或获取单独的图例

如何解决如何通过ggplot2中的构面对图例进行分组或获取单独的图例

我有一个数据集，该数据集按区域进行了分面显示，然后使用子区域作为填充。我已经使用与子区域名称相关的单独的命名变量定义了颜色。我想知道是否可以将图例本身以类似于构面的方式进行分组，以使其更易于解释。

命名的sub_region变量

sub_region_colours <- c("South America" = "#0570b0","Western Africa" = "#8c96c6","Central America" = "#74a9cf","Eastern Africa" = "#8856a7","Northern Africa" = "#edf8fb","Middle Africa" = "#b3cde3","Southern Africa" = "#810f7c","Northern America" = "#f1eef6","Caribbean" = "#bdc9e1","Eastern Asia" = "#bd0026","Southern Asia" = "#fd8d3c","South-Eastern Asia" = "#f03b20","Southern Europe" = "#238b45","Australia and New Zealand" = "#ce1256","Melanesia" = "#df65b0","Micronesia" = "#d7b5d8","Polynesia" = "#f1eef6","Central Asia" = "#fecc5c","Western Asia" = "#ffffb2","Eastern Europe" = "#66c2a4","Northern Europe" = "#edf8fb","Western Europe" = "#b2e2e2","Small Islands" = "#252525")

这是按sender_iso3分组的头（exporting_countries），已删除年份和sender_region。

structure(list(sender_iso3 = c("ABW","ABW","ABW"),year = c(2005,2011,2014,2015,2016,2017),sender_region = c("Americas","Americas","Americas"),sender_subregion = c("Caribbean","Caribbean","Caribbean"),export = c(1,1,4,5,2,1)),class = "data.frame",row.names = c(NA,-6L
))

最后这是当前情节的代码

  geom_bar()+
  labs(title = "Number of countries reporting export of chickens",fill = "Subregion")+
  facet_wrap(~ sender_region)+
  theme_minimal()+
  scale_x_continuous(name = "Year",limits = c(1986,breaks = c(1986,1990,2000,2010,guide = guide_axis(angle = 90))+
  scale_fill_manual(values = sub_region_colours)+
  guides(fill = guide_legend(ncol = 2))

此刻产生的是

Graph with less than ideal legend

如果我可以将图例填充颜色与刻面类似地进行分组，那将是一件很棒的事情，这将使其更易于阅读。

解决方法

一种实现此目的的方法是为每个区域绘制单独的图，并使用patchwork将图粘合在一起。第二种方法是利用ggnewscale软件包，该软件包允许在一个图中具有多个填充（或...）比例和图例。

但是，类似于使用patchwork的方法和使用ggnewscale包的方法可能会变得有些乏味，因为它需要根据构面数拆分数据并通过单独的图层绘制每个数据集。因此，我的解决方案添加了一个辅助函数，该函数1）分割数据并为每个区域或构面设置图层，然后2）可用于通过例如lapply。

顺便说一句：由于您的样本数据仅包含一个区域，因此我添加了第二个区域。

library(dplyr)
library(ggplot2)
library(ggnewscale)

sub_region_colours <- c("South America" = "#0570b0","Western Africa" = "#8c96c6","Central America" = "#74a9cf","Eastern Africa" = "#8856a7","Northern Africa" = "#edf8fb","Middle Africa" = "#b3cde3","Southern Africa" = "#810f7c","Northern America" = "#f1eef6","Caribbean" = "#bdc9e1","Eastern Asia" = "#bd0026","Southern Asia" = "#fd8d3c","South-Eastern Asia" = "#f03b20","Southern Europe" = "#238b45","Australia and New Zealand" = "#ce1256","Melanesia" = "#df65b0","Micronesia" = "#d7b5d8","Polynesia" = "#f1eef6","Central Asia" = "#fecc5c","Western Asia" = "#ffffb2","Eastern Europe" = "#66c2a4","Northern Europe" = "#edf8fb","Western Europe" = "#b2e2e2","Small Islands" = "#252525")

d <- structure(list(sender_iso3 = c(
  "ABW","ABW","ABW"
),year = c(
  2005,2011,2014,2015,2016,2017,2005,2017
),sender_region = c(
  "Americas","Americas","Africa","Africa"
),sender_subregion = c(
  "Caribbean","Caribbean","Southern Africa","Southern Africa"
),export = c(
  1,1,4,5,2,1
)),class = "data.frame",row.names = c(NA,-12L))
regions <- unique(d$sender_region)

# Layers for each region
make_layers <- function(x) {
  d <- filter(d,sender_region == regions[[x]])

  list(
    if (x != 1) new_scale_fill(),geom_bar(data = d,aes(x = year,fill = sender_subregion)),scale_fill_manual(
      values = sub_region_colours,guide = guide_legend(
        order = x,title = regions[x],title.position = "top"
      )
    )
  )
}
p <- ggplot() +
  lapply(seq_along(regions),make_layers)

# Add theme and wrap
p +
  theme_minimal() +
  scale_x_continuous(
    name = "Year",limits = c(1986,2017),breaks = c(1986,1990,2000,2010,guide = guide_axis(angle = 90)
  ) +
  facet_wrap(~sender_region)