如何调整Plotly subplot标题位置以避免被截断？

问题背景 #

使用plotly::subplot组合三个基于ggplot生成的气温趋势图后，主标题出现顶部截断的情况，无法完整显示。

修复方法 #

以下两种方法均可解决标题截断问题，按需选择：

方法1：精细化调整标题位置与边距

在layout()中对标题的垂直位置和内边距进行设置，同时为图表顶部预留足够空间：

p = subplot(AvgTMeanYearFP, AvgTMinYearFP, AvgTMaxYearFP, titleY = TRUE, shareX = TRUE, nrows = 3) %>% 
  layout(
    title = list(
      text = "Historic Average Temperature And Future Temperature Projection",
      y = 0.98,  # 控制标题垂直位置，值越大越靠近顶部
      pad = list(t = 20)  # 增加标题顶部内边距
    ),
    margin = list(t = 80)  # 增大图表顶部外边距，给标题预留显示空间
  )

方法2：直接增加顶部边距

如果不需要精细调整标题位置，仅通过增大顶部边距即可快速解决：

p = subplot(AvgTMeanYearFP, AvgTMinYearFP, AvgTMaxYearFP, titleY = TRUE, shareX = TRUE, nrows = 3) %>% 
  layout(
    title = "Historic Average Temperature And Future Temperature Projection",
    margin = list(t = 80)  # 替换默认较小的顶部边距
  )

完整修改后的代码 #

library(tidyverse)
library(plotly)

AvgTMeanYearFP = ggplot(df, aes(year, AvgTMean)) + 
  geom_smooth(method = 'lm', fullrange = TRUE) +
  annotate('rect', xmin = -Inf, xmax = 2021, ymin = -Inf, ymax = Inf,
           fill = 'gray92') +
  geom_vline(xintercept = seq(1980, 2020, 5), color = 'white') +
  geom_hline(yintercept = seq(23.5, 25.5, 0.5), color = 'white') +
  geom_line() +
  scale_x_continuous(limits = c(1980, 2030)) +
  labs(y = "Avg. Mean T (C)", x = "Year") +
  geom_text(aes(x = 2000 , y = 25.5, label = "Historic Trend")) +
  geom_text(aes(x = 2025 , y = 25.5, label = "Forecast Trend"))

AvgTMinYearFP = ggplot(df, aes(year, AvgTMin)) + 
  geom_smooth(method = 'lm', fullrange = TRUE) +
  annotate('rect', xmin = -Inf, xmax = 2021, ymin = -Inf, ymax = Inf,
           fill = 'gray92') +
  geom_vline(xintercept = seq(1980, 2020, 5), color = 'white') +
  geom_hline(yintercept = seq(23.5, 25.5, 0.5), color = 'white') +
  geom_line() +
  scale_x_continuous(limits = c(1980, 2030)) +
  ylim(18, 23) +
  labs(y = "Avg. Min. T (C)", x = "Year")

AvgTMaxYearFP = ggplot(df, aes(year, AvgTMax)) + 
  geom_smooth(method = 'lm', fullrange = TRUE) +
  annotate('rect', xmin = -Inf, xmax = 2021, ymin = -Inf, ymax = Inf,
           fill = 'gray92') +
  geom_vline(xintercept = seq(1980, 2020, 5), color = 'white') +
  geom_hline(yintercept = seq(23.5, 25.5, 0.5), color = 'white') +
  geom_line() +
  scale_x_continuous(limits = c(1980, 2030)) +
  ylim(27, 30) +
  labs(y = "Avg. Max. T (C)", x = "Year")

# 组合图表并应用标题调整（方法1）
p = subplot(AvgTMeanYearFP, AvgTMinYearFP, AvgTMaxYearFP, titleY = TRUE, shareX = TRUE, nrows = 3) %>% 
  layout(
    title = list(
      text = "Historic Average Temperature And Future Temperature Projection",
      y = 0.98,
      pad = list(t = 20)
    ),
    margin = list(t = 80)
  )

# 添加预测区域标记框
p$x$layout$shapes = list(type = "rect",
     fillcolor = "red", 
     opacity = 0.1,
     x0 = 2021, 
     x1 = 2030, 
     xref = "x", 
     y0 = 0, 
     y1 = 1, 
     yref = "paper")

p

内容的提问来源于stack exchange，提问作者Ed_Gravy