R语言Plotly绘制环形图时调整图例、扩大绘图区的实现方法

问题场景 #

使用Plotly绘制环形图时，若分类标签包含百字级长文本，默认图例配置会占用大量画布空间，挤压环形图本身的显示区域。要求在保留原有标题及对应字体设置不变的前提下，缩小图例占用空间、扩大环形图显示尺寸。
原实现代码如下：

library(plotly)
library(reshape2)
library(dplyr)

df<-data.frame(city=c("NYC-The written history of New York City began with the first European explorer, the Italian Giovanni da Verrazzano in 1524. European settlement began with the Dutch in 1608.",
                      "Seattle-Seattle is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. ",
                      "Boston",
                      "LA",
                      "Miami",
                      "Washington"),
               value=c(100,200,300,400,500,600))

df <-melt(df)

fig<-df %>% 
  plot_ly(labels = ~city, values = ~value)
fig <- fig %>% add_pie(hole = 0.6)
fig <- fig%>% layout(title = "Comparison between of the cities ")

fig

修复代码 #

核心调整分为三块：手动指定环形图绘制域、压缩图例占用空间、削减画布无效边距，全程不改动原有标题配置：

library(plotly)
library(reshape2)
library(dplyr)

df<-data.frame(city=c("NYC-The written history of New York City began with the first European explorer, the Italian Giovanni da Verrazzano in 1524. European settlement began with the Dutch in 1608.",
                      "Seattle-Seattle is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. ",
                      "Boston",
                      "LA",
                      "Miami",
                      "Washington"),
               value=c(100,200,300,400,500,600))

df <-melt(df)

fig<-df %>% 
  plot_ly(labels = ~city, values = ~value)
fig <- fig %>% add_pie(
  hole = 0.6,
  # 手动指定环形图绘制范围，仅给左侧图例预留窄幅空间
  domain = list(x = c(0.18, 0.98), y = c(0.02, 0.95))
)
fig <- fig%>% layout(
  title = "Comparison between of the cities ",
  # 图例布局优化
  legend = list(
    x = 0.01,
    y = 0.5,
    font = list(size = 9),
    itemwidth = 25
  ),
  # 压缩画布四周无效边距
  margin = list(l = 0, r = 0, t = 40, b = 0)
)

fig

关键调整说明 #

• 在add_pie中增加domain参数：手动定义环形图在画布上的坐标范围，打破默认自动排布给图例预留过宽空间的问题，直接扩大环形图的可显示尺寸
• 新增legend配置：将图例固定在画布最左侧垂直居中位置，缩小图例字号、限制图例条目宽度，超长文本自动换行，避免单条长文本撑满整列图例
• 配置margin参数：削减画布左右、底部的空白边距，仅保留顶部标题所需空间，进一步释放绘图区域
• 全程未修改原有标题的文本、字体相关配置，满足需求约束

内容的提问来源于stack exchange，提问作者silent_hunter