R中的分组ggplot箱线图

Question

对于示例数据框：

   df <- structure(list(year = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L), letter_group = c("A", "A", "A", "B", "B", "B", "C", 
"C", "C", "C", "A", "A", "A", "B", "B", "B", "C", "C", "C", "C", 
"A", "A", "A", "B", "B", "B", "C", "C", "C", "C", "C", "C", "C", 
"A", "A", "A", "B", "B", "B", "C", "C", "C", "C", "C"), value = c(2L, 
3L, 4L, 5L, 6L, 6L, 7L, 8L, 5L, 6L, 7L, 3L, 4L, 5L, 6L, 4L, 5L, 
6L, 2L, 3L, 4L, 4L, 5L, 6L, 7L, 8L, 5L, 3L, 2L, 4L, 5L, 6L, 4L, 
3L, 4L, 5L, 6L, 7L, 1L, 2L, 4L, 5L, 6L, 4L)), .Names = c("year", 
"letter_group", "value"), row.names = c(NA, -44L), class = c("tbl_df", 
"tbl", "data.frame"), spec = structure(list(cols = structure(list(
    year = structure(list(), class = c("collector_integer", "collector"
    )), letter_group = structure(list(), class = c("collector_character", 
    "collector")), value = structure(list(), class = c("collector_integer", 
    "collector"))), .Names = c("year", "letter_group", "value"
)), default = structure(list(), class = c("collector_guess", 
"collector"))), .Names = c("cols", "default"), class = "col_spec"))

我正在尝试创建一个箱线图，其中包含 x 轴上的年份 - 以及按年份分组的“字母组”...

即第 1 年的 A、B、C，然后是小空间，然后是第 2 年的 A、B C，依此类推....

我有以下几点：

library(ggplot2)

p1 <- ggplot(df, aes(year, value))
p1 + geom_boxplot(aes(group=letter_group))

但这只会产生 3 个箱形图。

有人可以帮帮我吗？

Answer 1

@nouse 的解决方案（这是最好的解决方案）的替代方案是使用刻面。但是，分面的一个好处是您还可以在 x 轴上获得字母组标签。

定义数据结构

# Load library
library(ggplot2)

# Define data frame
df <- structure(list(year = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
                              2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 
                              3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
                              4L, 4L), letter_group = c("A", "A", "A", "B", "B", "B", "C", 
                                                        "C", "C", "C", "A", "A", "A", "B", "B", "B", "C", "C", "C", "C", 
                                                        "A", "A", "A", "B", "B", "B", "C", "C", "C", "C", "C", "C", "C", 
                                                        "A", "A", "A", "B", "B", "B", "C", "C", "C", "C", "C"), 
                     value = c(2L, 3L, 4L, 5L, 6L, 6L, 7L, 8L, 5L, 6L, 7L, 3L, 4L, 5L, 6L, 4L, 5L, 
                               6L, 2L, 3L, 4L, 4L, 5L, 6L, 7L, 8L, 5L, 3L, 2L, 4L, 5L, 6L, 4L, 
                               3L, 4L, 5L, 6L, 7L, 1L, 2L, 4L, 5L, 6L, 4L)), 
                .Names = c("year", "letter_group", "value"), 
                row.names = c(NA, -44L), 
                class = c("tbl_df","tbl", "data.frame"), 
                spec = structure(list(cols = structure(list( ear = structure(list(), class = c("collector_integer", "collector")), 
                                                             letter_group = structure(list(), class = c("collector_character", "collector")), 
                                                             value = structure(list(), class = c("collector_integer",  "collector"))), 
                                                       .Names = c("year", "letter_group", "value")), 
                                      default = structure(list(), class = c("collector_guess", "collector"))), 
                                 .Names = c("cols", "default"), class = "col_spec"))

绘制结果

# Plot results
g <- ggplot(df)
g <- g + geom_boxplot(aes(letter_group, value))
g <- g + facet_grid(. ~ year, switch = "x")
g <- g + theme(strip.placement = "outside",
               strip.background = element_blank(),
               panel.background = element_rect(fill = "white"),
               panel.grid.major = element_line(colour = alpha("gray50", 0.25), linetype = "dashed"))
g <- g + ylab("Value") + xlab("Year & Letter Group")
print(g)

^{由reprex package (v0.2.1) 于 2019 年 5 月 23 日创建}

Answer 2

here，您的问题已基本得到解答。

您的数据框不包含因子，因此您首先需要将分组变量转换为因子。然后，根据上面给出的链接，有两个选项。要么通过组合你的两个原始因子来构建一个新因子（如 z-cool 的答案所示） - 但这不会在 x 轴上的因子水平之间创建所需的空间 - 或者你需要将你的因子之一分配给 @ 987654322@，或col。就您而言，解决问题的最快方法是

ggplot(df, aes(as.factor(year), value, fill=as.factor(letter_group))) + geom_boxplot()

如果您不想为绘图着色，可以使用scale_fill_manual 或scale_color_manual 更改此设置，具体取决于您之前在aes 中的选择：

ggplot(df, aes(as.factor(year), value, fill=as.factor(letter_group))) + geom_boxplot() +
  scale_fill_manual(values=c("white", "white", "white")) +
  theme(legend.position = "none")

Answer 3

这应该可以工作

library(tidyverse)
df %>% 
  mutate(year_group = paste(year, letter_group)) %>% 
  ggplot(aes(year_group, value)) +
  geom_boxplot()