ggplot添加的文本标签无法显示问题求助

问题根源 #

你设置的ymin = 250大概率超出了当前图表y轴的实际最大值，导致文本被放置在绘图区域之外；即便开启了coord_cartesian(clip = "off")，如果顶部没有预留足够边距，依然看不到文本。另外annotation_custom对于按年份标注的场景，不如geom_text灵活可控。

方案一：调整annotation_custom参数与图表边距 #

pub_over_year <- as_tibble(S$AnnualProduction) %>% 
  ggplot(aes(x = Year, y = Articles, group = 1)) +
  geom_point() +
  geom_line()+
  labs(x = "Years", y = "Number of publications") +
  geom_text(aes(label= Articles), hjust= 0.5, vjust = -2, size= 3, color= "black") +
  # 动态获取y轴最大值，将文本放在最大值上方
  annotation_custom(grid::textGrob("event 1", rot = 90), 
                    xmin = 2010, xmax = 2010, 
                    ymin = max(S$AnnualProduction$Articles) + 10) +
  annotation_custom(grid::textGrob("event 2", rot = 90), 
                    xmin = 2011, xmax = 2011, 
                    ymin = max(S$AnnualProduction$Articles) + 10) +
  coord_cartesian(clip = "off") +
  theme_minimal() +
  # 增加顶部边距，让文本显示出来
  theme(plot.margin = margin(t = 30, r = 10, b = 10, l = 10))
pub_over_year

方案二：用geom_text实现（推荐） #

先创建事件数据框，直接通过geom_text绘制，无需依赖annotation_custom：

# 构建事件数据
events <- tibble(
  Year = c(2010, 2011),
  Event = c("event 1", "event 2"),
  # 将文本位置设为y轴最大值上方固定偏移量
  y_pos = max(S$AnnualProduction$Articles) + 10
)

pub_over_year <- as_tibble(S$AnnualProduction) %>% 
  ggplot(aes(x = Year, y = Articles, group = 1)) +
  geom_point() +
  geom_line()+
  labs(x = "Years", y = "Number of publications") +
  geom_text(aes(label= Articles), hjust= 0.5, vjust = -2, size= 3, color= "black") +
  # 添加事件文本并旋转90度
  geom_text(data = events, aes(x = Year, y = y_pos, label = Event), 
            angle = 90, hjust = 0, size = 3) +
  coord_cartesian(clip = "off") +
  theme_minimal() +
  theme(plot.margin = margin(t = 30, r = 10, b = 10, l = 10))
pub_over_year

以上两种方式都能让事件文本显示在图表顶部对应年份的位置，且通过动态获取y轴最大值，可适配不同的数据范围，避免位置偏差。

内容的提问来源于stack exchange，提问作者Andrea