简介
这篇推文代码来源于：TidyTuesday[1]，主要想学习如何绘制灯芯柱状图（名字小编瞎取的），最终结果如下：
注释：与普通柱状图相比，灯芯柱状图不仅可以展示随时间变化的总体趋势（图中黑色柱子 "Rescues"），而且能够清晰展示灯芯内部数据（图中浅灰色柱子 "cats"）相对于总体的比例随时间的变化。
看到最终成品，读者是否可以根据自己所学知识，回答以下几个问题：
- 如何实现两个柱状图嵌套？
- 如何使得2020年份数据单独显示为粉色？
- 如何在柱状图上方添加文字，其中一些文字包括其他单词？
接下来，小编带你解读源代码，并回答以上问题。读者可以根据这些知识要点，灵活应用到其他图形中。
数据介绍
从文件 animal_rescues.txt 中读取数据，并对数据进行预处理，包括分类汇总和计数。
注意：由于时间和文章篇幅原因，数据处理部分不做过多介绍。读者可以根据格式，使用自己比较感兴趣的数据。
library(tidyverse) library(ggtext) library(ggrepel) library(patchwork) library(systemfonts)
# 数据读取+处理 ======== df_animals <- readr::read_csv('animal_rescues.txt') df_animals_agg <- df_animals %>% mutate( animal_group_aggregated = case_when( str_detect(animal_group_parent, "Domestic|Livestock|Farm|Horse|Cow|Sheep|Goat|Lamb|Bull") ~ "Other Domestic Animals", animal_group_parent %in% c("Cat", "cat") ~ "Cats", animal_group_parent %in% c("Bird", "Budgie") ~ "Birds", animal_group_parent == "Dog" ~ "Dogs", animal_group_parent == "Fox" ~ "Foxes", TRUE ~ "Other Wild Animals" ) ) %>% count(cal_year, animal_group_aggregated) %>% group_by(animal_group_aggregated) %>% mutate( total = sum(n), current = n[which(cal_year == 2021)] ) %>% ungroup() %>% mutate( animal_group_aggregated = fct_reorder(animal_group_aggregated, total), animal_group_aggregated = fct_relevel(animal_group_aggregated, "Other Domestic Animals", after = 0), animal_group_aggregated = fct_relevel(animal_group_aggregated, "Other Wild Animals", after = 0) ) df_animals_labs <- df_animals_agg %>% filter(cal_year == 2016) %>% group_by(animal_group_aggregated) %>% mutate(n = case_when( animal_group_aggregated == "Cats" ~ 320, animal_group_aggregated %in% c("Birds", "Dogs") ~ 135, TRUE ~ 55 )) df_animals_annotate <- df_animals_agg %>% mutate(label = "\n\n← Number of Rescues in 2021 so far.") %>% filter(cal_year == 2021 & animal_group_aggregated == "Cats") df_animals_sum <- df_animals_agg %>% filter(cal_year < 2021) %>% group_by(cal_year) %>% summarize(n = sum(n))
绘图主要使用 df_animals_sum，以下是该数据预览：
画图
绘图代码使用了 R 中的多个包（tidyverse, ggtext, ggrepel, patchwork, systemfonts）来创建一个特定风格的统计图表。以下是代码的主要步骤和功能：
设置主题和风格：
设置基础主题为 theme_minimal，指定了基本字体大小和字体家族。使用 theme_update 对不同图表元素进行自定义，包括文本样式、轴样式、网格线样式等。
# 主题设置 ====== theme_set(theme_minimal(base_size = 19)) # 自定义主题细节 theme_update( text = element_text(color = "grey12"), axis.title = element_blank(), axis.text.x = element_text(), axis.text.y = element_blank(), panel.grid.major.y = element_blank(), panel.grid.minor = element_blank(), plot.margin = margin(20, 5, 10, 10), plot.subtitle = element_textbox_simple(size = 14, lineheight = 1.6), plot.title.position = "plot", plot.caption = element_text( color = "#b40059", hjust = .5, size = 10, margin = margin(35, 0, 0, 0)) )
数据可视化
为了更好解读代码中的细节部分，小编将代码进行分解，一步步展示细节内容。完整绘图代码见文末，或者可以在我的 Github[2] 中找到源代码和数据。
- 创建一个柱状图 (
geom_col) 表示不同年份的动物救援数量。
df_animals_sum %>% ggplot(aes(cal_year, n)) + geom_col(aes(fill = factor(cal_year)), width = .85)
- 再添加一个柱状图，指定
data和fill参数，并通过修改width实现嵌套（问题一答案）。这里数据进行过滤，选择 2021 年前数据，并且选择animal_group_aggregated == "Cats"。另一个细节：alpha = cal_year == 2020透明度根据是否cal_year==2000进行设置。如果是则 fill = "white"。
geom_col( data = df_animals_agg %>% filter(animal_group_aggregated == "Cats" & cal_year < 2021), aes(alpha = cal_year == 2020), # 这里有细节！ fill = "white", width = .5 # 宽度和透明度设置 )
加入该代码后，绘图结果为：
- 使用
geom_text在图上添加文本标签。对数据进行处理，添加新列文本数据，实现添加其他文字（问题三答案）。df_animals_sum %>% mutate(n_lab = if_else(cal_year %in% c(2009, 2020), paste0(n, "\nRescues"), as.character(n)))。
geom_text( #添加文本+加入rescues data = df_animals_sum %>% mutate(n_lab = if_else(cal_year %in% c(2009, 2020), paste0(n, "\nRescues"), as.character(n))), aes(label = n_lab), size = 4.3, lineheight = .8, nudge_y = 12, vjust = 0, color = "grey12", fontface = "bold" ) + geom_text( #添加文本+加入cats data = df_animals_agg %>% filter(animal_group_aggregated == "Cats" & cal_year < 2021) %>% mutate(n_lab = if_else(cal_year %in% c(2009, 2020), paste0(n, "\nCats"), as.character(n))), aes(label = n_lab), color = "white", lineheight = .8, size = 4.3, nudge_y = 12, vjust = 0, fontface = "bold" ) + geom_text( # 手动添加年份标签 data = df_animals_agg %>% filter(animal_group_aggregated == "Cats" & cal_year < 2021), aes(y = -15, label = cal_year, color = factor(cal_year)), size = 6, hjust = .5, vjust = 1 )
- 调整图表样式：自定义图表的标题、副标题、图例等元素的样式。通过
scale_fill_manual(values = c(rep("grey30", 11), "#b40059"), guide = "none")实现手动颜色填充，突出 2020 年数据（问题二答案）。
coord_cartesian(clip = "off") + scale_y_continuous(limits = c(-15, NA)) + scale_color_manual(values = c(rep("grey30", 11), "#b40059"), guide = "none") + scale_fill_manual(values = c(rep("grey30", 11), "#b40059"), guide = "none") + scale_alpha_manual(values = c(.25, .4), guide = "none") + theme( # plot.title = element_markdown(size = 28, margin = margin(5, 35, 25, 35), color = "black"), # plot.subtitle = element_textbox_simple(margin = margin(5, 35, 15, 35)), panel.grid.major = element_blank(), axis.text.x = element_blank() )
最终结果如下：
绘图完整代码
df_animals_sum %>% ggplot(aes(cal_year, n)) + geom_col(aes(fill = factor(cal_year)), width = .85) + geom_col( data = df_animals_agg %>% filter(animal_group_aggregated == "Cats" & cal_year < 2021), aes(alpha = cal_year == 2020), # 这里有细节！ fill = "white", width = .5 # 宽度和透明度设置 ) + geom_text( #这里的数据处理：添加文本+加入rescues data = df_animals_sum %>% mutate(n_lab = if_else(cal_year %in% c(2009, 2020), paste0(n, "\nRescues"), as.character(n))), aes(label = n_lab), size = 4.3, lineheight = .8, nudge_y = 12, vjust = 0, color = "grey12", fontface = "bold" ) + geom_text( #添加文本+加入cats data = df_animals_agg %>% filter(animal_group_aggregated == "Cats" & cal_year < 2021) %>% mutate(n_lab = if_else(cal_year %in% c(2009, 2020), paste0(n, "\nCats"), as.character(n))), aes(label = n_lab), color = "white", lineheight = .8, size = 4.3, nudge_y = 12, vjust = 0, fontface = "bold" ) + geom_text( # 手动添加年份标签 data = df_animals_agg %>% filter(animal_group_aggregated == "Cats" & cal_year < 2021), aes(y = -15, label = cal_year, color = factor(cal_year)), size = 6, hjust = .5, vjust = 1 ) + coord_cartesian(clip = "off") + scale_y_continuous(limits = c(-15, NA)) + scale_color_manual(values = c(rep("grey30", 11), "#b40059"), guide = "none") + scale_fill_manual(values = c(rep("grey30", 11), "#b40059"), guide = "none") + scale_alpha_manual(values = c(.25, .4), guide = "none") + theme( # plot.title = element_markdown(size = 28, margin = margin(5, 35, 25, 35), color = "black"), # plot.subtitle = element_textbox_simple(margin = margin(5, 35, 15, 35)), panel.grid.major = element_blank(), axis.text.x = element_blank() )
参考资料
[1]
TidyTuesday: https://github.com/z3tt/TidyTuesday/blob/main/R/2021_27_AnimalRescues.Rmd
[2]
Github: https://github.com/liangliangzhuang/R_example
