ggplot柱状图多图例字号过大，如何统一设置为7号？

问题 #

我绘制的柱状图因左侧、右侧及底部的文本字号过大导致显示效果不佳。尝试用legend.title = element_text(size=7)仅成功修改了右侧“Answer”图例的标题字号，希望将图中所有文本统一设置为该字号。此前错误将这段代码放入scale_y_continuous参数中，触发报错：

Error in scale_y_continuous(name = "Percentage", breaks = seq(from = 0,  :  unused argument (legend.title = element_text(size = 7))

请问正确的代码放置位置或是否需要其他代码？

原代码 #

mydata %>%
  mutate(
    variable = recode(
      variable,
      'item3' = '
      Very long item name here')) %>%
  drop_na() %>%
  ggplot(mapping = aes(x = variable)) +
  geom_bar(aes(fill = value),
           position = 'fill',
           width = 0.30)+
  scale_y_continuous(name = 'Percentage',
                     breaks = seq(from = 0, to = 1, by = 0.2),
                     minor_breaks = seq(from = 0, to = 1, by = 0.1),
                     labels = seq(from = 0, to = 100, by = 20),
                     expand = c(0,0)) +
  xlab( element_blank() ) +
  scale_fill_manual(
    values = c(fioh_colors$fioh_blue_40,
               fioh_colors$fioh_blue_60,
               fioh_colors$fioh_blue_80,
               fioh_colors$fioh_blue_100,
               fioh_colors$fioh_turq_20
    ),
    labels = c(
      'yes',
      'no',
      'maybe'
    ),
    drop = FALSE
  ) +
  guides(
    fill = guide_legend(title = 'Answer')
  ) + theme(panel.background = element_blank(),
            legend.title = element_text(size=7),
            plot.margin = margin(t = 30, r =  30, b = 20, l = 0),
            axis.ticks.y = element_blank(),
            panel.grid.major = element_line(colour = 'grey'),
            axis.ticks.x = element_line(colour = 'grey'),
            panel.grid.minor = element_line(colour = 'lightgrey'),
            axis.text.y = element_text(
              size = 11,
              face = 'bold',
              hjust = 0
            )) +
  coord_flip()

数据 #

structure(list(variable = c("item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3", 
"item3", "item3", "item3", "item3", "item3", "item3", "item3"), value = structure(c(1L, 1L, 2L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 3L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 
1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 2L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 
2L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 1L, 2L, 1L, 2L, 1L, 1L, 2L, 
1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L), .Label = c("1", 
"2", "3"), class = c("ordered", "factor"))), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -147L))

解决方案 #

所有文本样式的调整都需要在theme()函数内完成，你只修改了图例标题的字号，还需要补充以下几个元素的设置：

• axis.text: 轴刻度文本（对应左侧、底部的刻度文字）
• axis.title: 轴标题（对应底部的"Percentage"）
• legend.text: 图例选项文本（对应右侧"Answer"下的yes/no/maybe）

修改后的完整代码如下：

mydata %>%
  mutate(
    variable = recode(
      variable,
      'item3' = 'Very long item name here')) %>%  # 去掉多余换行避免文本异常
  drop_na() %>%
  ggplot(mapping = aes(x = variable)) +
  geom_bar(aes(fill = value),
           position = 'fill',
           width = 0.30)+
  scale_y_continuous(name = 'Percentage',
                     breaks = seq(from = 0, to = 1, by = 0.2),
                     minor_breaks = seq(from = 0, to = 1, by = 0.1),
                     labels = seq(from = 0, to = 100, by = 20),
                     expand = c(0,0)) +
  xlab(element_blank()) +
  scale_fill_manual(
    values = c(fioh_colors$fioh_blue_40,
               fioh_colors$fioh_blue_60,
               fioh_colors$fioh_blue_80,
               fioh_colors$fioh_blue_100,
               fioh_colors$fioh_turq_20
    ),
    labels = c(
      'yes',
      'no',
      'maybe'
    ),
    drop = FALSE
  ) +
  guides(
    fill = guide_legend(title = 'Answer')
  ) + 
  theme(
    panel.background = element_blank(),
    # 统一设置所有文本字号为7
    legend.title = element_text(size=7),
    legend.text = element_text(size=7),
    axis.text = element_text(size=7),
    axis.title = element_text(size=7),
    plot.margin = margin(t = 30, r =  30, b = 20, l = 0),
    axis.ticks.y = element_blank(),
    panel.grid.major = element_line(colour = 'grey'),
    axis.ticks.x = element_line(colour = 'grey'),
    panel.grid.minor = element_line(colour = 'lightgrey'),
    # 保留y轴文本加粗样式，仅修改字号
    axis.text.y = element_text(
      size = 7,
      face = 'bold',
      hjust = 0
    )
  ) +
  coord_flip()

关键说明 #

1. 之前报错是因为scale_y_continuous仅负责坐标轴的刻度、标签等逻辑设置，不接受主题样式参数，所有主题相关的设置必须放在theme()中。
2. 若不需要y轴文本的加粗样式，可以直接删除axis.text.y的单独设置，让它继承axis.text的统一样式。
3. 修正了variable重编码时的多余换行，避免左侧文本出现不必要的空白。

内容的提问来源于stack exchange，提问作者Espejito