如何在ggplot中为指定坐标轴标签添加空白间隔？

要在普通标签和加粗标签之间添加空白间隔，同时不修改原dataframe，可通过在x轴因子水平中插入一个无数据的空类别实现，具体修改如下：

修改后的完整代码 #

plot_data <- data.frame(
    Evaluation = rep(c("A", "B", "C"), each = 4),
    Mittari = rep(c("M1", "M2", "M3", "M4"), times = 3),
    value = runif(12),
    Kansallinen = runif(12)
)

custom_labels <- c("\"Are you happy?\"", "\"Are you sad?\"", "\"Is the student happy?\"", "\"Is the student sad?\"")
ss <- data.frame(Mittari = unique(plot_data$Mittari), custom_label = c("Yes", "Yes", "Agree", "Agree"))
plot_data <- plot_data %>%
    left_join(ss, by = "Mittari")


ggplot(plot_data, aes(x = factor(Mittari, levels = c("M1", "M2", "space", "M3", "M4")), y = value, fill = Evaluation)) +
    geom_bar(stat = "identity", position = position_dodge2(reverse = TRUE, width = 0.45)) +
    geom_vline(aes(xintercept = 0, color = 'National average')) +
    geom_errorbar(aes(ymin = Kansallinen, ymax = Kansallinen, group = Evaluation, width = 0.45), 
                  position = position_dodge2(reverse = TRUE)) +
    geom_text(aes(group = Mittari, y = 0.35, label = custom_label), size = 3.3, hjust = 0.5, vjust = -2.1, colour = "grey8") +
    scale_fill_manual(values = c("steelblue", "darkorange", "lightgreen")) +
    scale_color_manual(values = c("black", "steelblue", "darkorange")) +
    theme_minimal() +
    coord_flip() +
    scale_y_continuous(labels = scales::percent_format(scale = 100),
                       breaks = seq(0, 1, by = 0.1),
                       minor_breaks = NULL,
                       limits = c(0, 1)) +
    scale_x_discrete(labels = c(custom_labels[1:2], "", custom_labels[3:4]),
                     limits = c("M1", "M2", "space", "M3", "M4")) +
    labs(y = "", x = NULL, color = NULL) +
    guides(fill = guide_legend(order = 1),
           color = guide_legend(order = 2)) +
    theme(axis.text.y = element_text(face = c("plain", "plain", "plain", "bold", "bold"), color = "black"))

关键修改点 #

• 插入空类别：将x轴的Mittari转换为包含空水平"space"的因子，在M2和M3之间生成无数据的位置，自然留出空白
• 设置空标签：在scale_x_discrete中把空水平的标签设为空字符串，避免显示多余内容
• 调整字体样式：更新axis.text.y的face参数，对应五个水平分别设置字体样式（前两个普通，中间空水平不影响，后两个加粗）

这种方法无需修改原dataframe结构，同时保证同类标签（M1-M2、M3-M4）之间的间距与原图表一致，仅在两类标签间增加空白。

内容的提问来源于stack exchange，提问作者Billyboy