条形图（bar chart）是用宽度相同的条形的高度或长短来表示数据多少的图形。成对比较的条形图很浅显易懂的展示两组数据的占比情况。下面我们用ggplot2绘制演示：

演示数据下载下载

# 加载R包
library(tidyverse)
library(ggthemes)

# 读取演示数据，中文数据读取
data <- read.csv("data.csv", header = T, encoding = "UTF-8")

# 绘图
data %>%
  ggplot(aes(x = level, fill = gender)) +
  # 建立第一组条形图
  geom_col(data = filter(x, gender == "男"),
           aes(y = percent)) +
  # 建立另一组条形图
  geom_col(data = filter(x, gender == "女"),
           aes(y = -1 * percent)) +
  # 建立第一组条形图标签
  geom_text(data = filter(x, gender == "男"),
            aes(y = percent, label = percent),
            hjust = -.1) +
  # 建立另一组条形图标签
  geom_text(
    data = filter(x, gender == "女"),
    aes(y = -1 * percent, label = percent),
    hjust = 1.1
  ) +
  # 设置y轴范围
  expand_limits(y = c(-17, 17)) +
  # 替换Y轴标签，用绝对值表示
  scale_y_continuous(breaks = seq(-15, 15, by = 5),
                     labels = abs) +
  # 轴翻转
  coord_flip() +
  # 主题
  theme_few() +
  # 图例位置
  guides(fill = guide_legend(title = '')) +
  theme(legend.position="top") +
  labs(
    x = "教育水平",
    y = "人群中所占比例",
    fill = "Gender",
    title = paste0("20XX年最高教育程度人口百分比")
  )

绘图中间用到了分别建立两组条形图通过拼接实现比较，其中coord_flip()做了x轴和y轴翻转，其他部分和常规的ggplot2基本操作一致。

参考资料：

1.https://www.r-bloggers.com/writing-functions-to-automate-repetitive-plotting-tasks-in-ggplot2/

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