如何调整column()内Plotly图表的标题对齐方式及与图表的间距

两个需求都可以通过调整plotly的layout配置实现：

• 标题左对齐：将原layout中的title参数从纯字符串改为列表结构，设置x = 0即可实现完全左对齐，默认值0.5为居中对齐
• 调整标题与图表间距：在title列表中添加pad参数，通过b字段控制标题底部与图表顶部的间距，数值越大间距越大，也可配合全局margin参数的t字段调整图表整体顶部边距，避免标题被截断

修改后的完整可运行代码如下：

library(shiny)
library(plotly)
library(shinydashboard)
x <- c('Product A', 'Product B', 'Product C')
y <- c(20, 14, 23)
text <- c('27% market share', '24% market share', '19% market share')
data <- data.frame(x, y, text)

ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(),
  dashboardBody(
    fluidRow(
     column(4,
            plotlyOutput("plot"))
      ),
    
  )
)

server <- function(input, output) { 
  output$plot<-renderPlotly({
    fig <- plot_ly(data, x = ~x, y = ~y, type = 'bar',
                   text = y, textposition = 'outside',
                   # rotate label
                   textangle = 90,
                   marker = list(color = 'rgb(158,202,225)',
                                 line = list(color = 'rgb(8,48,107)', width = 1.5)))
    fig <- fig %>% layout(
      title = list(
        text = paste("Cumulative Uptake (%) of the first vaccine dose among adults (18+) in EU/EEA countries","as of 2021-04-05",sep="\n"),
        x = 0, # 左对齐配置
        pad = list(b = 15) # 标题底部和图表的间距，可自行调整数值
      ),
      titlefont = list(size = 12),
      margin = list(t = 70), # 图表整体顶部边距，可根据标题长度自行调整
      xaxis = list(fixedrange=T, title = ""),
      yaxis = list(fixedrange=T,title = ""))
    
    fig
  })
}

shinyApp(ui, server)

内容的提问来源于stack exchange，提问作者firmo23