如何将图例组织到子组中？

Question

我的条形图的图例当前在一个长列表中列出了该图中的所有项目。我希望每个列都有图例组本身。

列数是动态的，因此图例必须能够相应地进行调整。

library("phyloseq"); packageVersion("phyloseq")
library(ggplot2)
library(scales)
data("GlobalPatterns")
TopNOTUs <- names(sort(taxa_sums(GlobalPatterns), TRUE)[1:50])
gp.ch   <- prune_species(TopNOTUs, GlobalPatterns)
gp.ch = subset_taxa(gp.ch, Genus != "NA")
mdf = psmelt(gp.ch)
# Create a ggplot similar to
library("ggplot2")
mdf$group <- paste0(mdf$Phylum, "-", mdf$Genus, sep = "")

colours <-ColourPalleteMulti(mdf, "Phylum", "Genus")

# Plot resultss
ggplot(mdf, aes(Phylum)) + 
  geom_bar(aes(fill = group), colour = "grey", position = "stack")

现在，图例打印以下项目：

放线菌-双歧杆菌

放线杆菌-罗氏菌

拟杆菌-泽泻

类杆菌

..。

我希望它打印出来：

放线菌

-Bifidobacterium

-Rothia

细菌

-Alistipes

-Bacteroides

..。

Answer 1

这有点老生常谈，但可能对你有用。首先，使用mtcars dataset将虚拟行添加到表示分组的数据中，然后为每个分组和组件类别分配一个因子级别。最后，我修改了图例中的alpha，这样分组标题就有了透明的颜色并且看起来是隐藏的。

# Fake data sample
library(tidyverse)
cars_sample <- mtcars %>%
  rownames_to_column(var = "name") %>%
  mutate(make = word(name, end = 1),
         model = word(name, start = 2, end = -1)) %>%
  filter(make %in% c("Mazda", "Merc", "Hornet")) %>%
  select(name, make, model, mpg, wt)


# Add rows for groups and make a factor for each group and each component
cars_sample_fct <- cars_sample %>%
  bind_rows( cars_sample %>% count(make) %>% mutate(model = make, name = "")) %>%
  arrange(make, name) %>%
  mutate(name_fct   = fct_inorder(if_else(name == "", make, paste0("- ", model))))

# Plot with transparent grouping legend labels
ggplot(cars_sample_fct, aes(wt, mpg, color = name_fct)) +
  geom_point() +
  scale_color_discrete(name = "Car") +
  guides(color = guide_legend(
    override.aes = list(size = 5, 
                        alpha = cars_sample_fct$name != "")))

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