ggplot中X轴列名相同时如何仅在单个X值添加数据点？

本人完全不懂编程，若表述有误还请见谅。我正在使用R语言通过ggplot绘图，现有数据集的图表已绘制完成，想要手动添加误差棒，但数据集不符合需求，打算先添加均值数据点再基于该点制作误差棒。但由于X轴值相同，数据点被添加到了每个分面列中。附上代码：

ggplot(well_data4, aes(x = E2F4, y = Colonies, color = Clone, fill = E2F4)) +
  geom_point(aes(color = Clone), size = 2) +
  geom_point(aes(x=("-/-"), y=2837.3333, color = "black")) +
  labs(title = "HT29 Colony Survival",
       x = "Concentration of SN-38 (nM)",
       y = "Number of colonies") + scale_color_manual(values = c('11' = "darkturquoise", "7" =     "darkturquoise", "2" = "darkturquoise","Control"= "darkorchid")) +
 scale_fill_discrete(labels = c("-/- = E2F4 Knockout", "+/+ = E2F4 Wild Type")) +
 guides(color = guide_legend(override.aes = list(size=3)), fill = guide_legend(override.aes =list(size=2))) +
facet_wrap(~Well, nrow = 1, strip.position = "bottom") +
theme_minimal() + 
theme(strip.placement = "outside", panel.spacing = unit(0, "cm"),  
    strip.text = element_text(size = 10, margin = margin(b=15)),  
    legend.title = element_text(size = 10),
    plot.title = element_text(margin = margin(b=10)))

我曾尝试添加该行代码：geom_point(aes(x=("-/-"), y=2837.3333, color = "black"))，还试图指定仅在"0"对应的分面列添加，但操作始终无效，恳请帮忙解决！

问题出在你用了facet_wrap(~Well)做分面，默认情况下geom_point会在所有分面里重复绘制这个手动点。要让它只出现在指定的Well（比如Well=0）分面中，需要给这个手动点指定对应的Well值，同时把颜色参数移出映射范围：

关键修改点 #

替换原来的手动点代码为：

geom_point(data = data.frame(Well = "0", E2F4 = "-/-", Colonies = 2837.3333), 
           aes(x = E2F4, y = Colonies), color = "black", size = 2)

完整代码 #

ggplot(well_data4, aes(x = E2F4, y = Colonies, color = Clone, fill = E2F4)) +
  geom_point(aes(color = Clone), size = 2) +
  # 指定分面的手动均值点
  geom_point(data = data.frame(Well = "0", E2F4 = "-/-", Colonies = 2837.3333), 
             aes(x = E2F4, y = Colonies), color = "black", size = 2) +
  labs(title = "HT29 Colony Survival",
       x = "Concentration of SN-38 (nM)",
       y = "Number of colonies") + 
  scale_color_manual(values = c('11' = "darkturquoise", "7" = "darkturquoise", 
                                "2" = "darkturquoise","Control"= "darkorchid")) +
  scale_fill_discrete(labels = c("-/- = E2F4 Knockout", "+/+ = E2F4 Wild Type")) +
  guides(color = guide_legend(override.aes = list(size=3)), 
         fill = guide_legend(override.aes = list(size=2))) +
  facet_wrap(~Well, nrow = 1, strip.position = "bottom") +
  theme_minimal() + 
  theme(strip.placement = "outside", panel.spacing = unit(0, "cm"),  
        strip.text = element_text(size = 10, margin = margin(b=15)),  
        legend.title = element_text(size = 10),
        plot.title = element_text(margin = margin(b=10)))

补充：添加误差棒 #

如果要基于这个均值点加误差棒，同样用geom_errorbar并传入相同的小数据集即可：

geom_errorbar(data = data.frame(Well = "0", E2F4 = "-/-", Colonies = 2837.3333, 
                                ymin = 2500, ymax = 3100),
              aes(x = E2F4, ymin = ymin, ymax = ymax), color = "black", width = 0.2)

内容的提问来源于stack exchange，提问作者astaf