arrangeGrob() 和类似的替代方法不接受 grobs 列表。在 grid.draw 处，返回： gList(...) 中的错误：“gList”中仅允许“grobs”

Question

我正在根据调查数据绘制大量图表，需要将每个问题的完整文本显示在生成的条形图旁边。排列网格似乎是做到这一点的最佳方法。但是，我尝试了几个包，并且在网格排列步骤中遇到了同样的问题，无法在 grid.draw() 步骤中将 grobs 的输入列表识别为 grobs。

手动输入每个 grob 的列表引用效果很好，但这不是一个可接受的解决方案，因为绘图量要求自动化过程。

# Dummy data set
question <- c("Q1. A very long text like this one is hard to use as a label.",
              "Q2. A very long text like this one is hard to use as a label.",
              "Q3. A very long text like this one is hard to use as a label.",
              "Q4. A very long text like this one is hard to use as a label.",
              "Q5. A very long text like this one is hard to use as a label.")

variable <- c("V1","V2")
set.seed(42)
response <- round(runif(n = length(question) * length(variable), min = 1, max = 10), 0)

# Create a data frame
df_example <- expand.grid(Question = question, Variable = variable)
df_example$Response <- rep(response, length.out = nrow(df_example))

grob_list <- list()
for (question in unique(df_example$Question)) {
  
  # Text grob
  # used textbox_grob() over alternatives for ease of wrapping text.
  text_grob <- textbox_grob(question, x = 0.05, y = 0.5, hjust = 0, vjust = 0.5, gp = gpar(col = "black"),
                            maxwidth = 1,
                            padding = unit(c(0, 20, 0, 0), "pt"))  
  # Bar chart
  bar_chart <- ggplot(df_example, aes(x = Variable, y = Response, fill = Variable)) +
    geom_bar(stat = "identity", position = "dodge") +
    coord_flip() +
    theme_minimal() +
    theme(legend.position = "none") +
    theme(axis.title.x = element_blank()) +
    theme(axis.title.y = element_blank())

  # Convert ggplot to grob
  bar_grob <- ggplotGrob(bar_chart)
  
  # Add text and bar chart grobs to the list of grobs
  grob_list[[length(grob_list) + 1]] <- list(text_grob, bar_grob)
}

### a. Required step for automation-
# Arrange grobs from list into a grid
combined_grobs <- arrangeGrob(grob = grob_list, ncol = 2)
# returns an error at grid.draw(): 
# > Error in gList(...) : only 'grobs' allowed in "gList"


### b. Manual step that works but not practical at scale-
# Arrange grobs manually using arrangeGrob from grid
combined_grobs <- arrangeGrob(grob_list[[1]][[1]], grob_list[[1]][[2]], 
                              grob_list[[2]][[1]], grob_list[[2]][[2]],
                              grob_list[[3]][[1]], grob_list[[3]][[2]],
                              grob_list[[4]][[1]], grob_list[[4]][[2]],
                              grob_list[[5]][[1]], grob_list[[5]][[2]],
                              ncol = 2
                              )

# Display after step a or b above. 
grid.newpage()
grid.draw(combined_grobs)

Answer 1

更简单的方法是使用分面和

ggtext::element_textbox(_simple)

自动换行问题文本：

library(ggplot2)
library(ggtext)

ggplot(df_example, aes(y = Variable, x = Response, fill = Variable)) +
  geom_bar(stat = "identity", position = "dodge") +
  facet_wrap(~Question, ncol = 1, strip.position = "left") +
  theme_minimal() +
  theme(
    legend.position = "none",
    axis.title.x = element_blank(),
    axis.title.y = element_blank(),
    strip.text.y.left = ggtext::element_textbox_simple(
      hjust = 0,
      padding = unit(c(0, 20, 0, 0), "pt")
    ),
    strip.placement = "outside"
  )