Shiny中Y轴使用对数转换后绘图点点击交互失效如何解决

问题原因 #

nearPoints 默认直接用原始数据集的坐标值匹配点击事件返回的坐标，而你给Y轴应用自定义的reverselog_trans转换后，绘图实际使用的是转换后的坐标空间，点击事件返回的y值是转换后的数值，和原始数据的plot列数值不一致，因此无法识别到点位。

修复方案 #

无需修改现有绘图配置，仅需要在调用nearPoints时，通过ytrans参数传入你自定义的反向对数转换函数，让nearPoints自动完成坐标转换匹配即可。

修改点 #

仅调整server中renderTable部分的代码：

output$data <- renderTable({
    req(input$plot_click)
    nearPoints(pretend_data, input$plot_click, ytrans = reverselog_trans(10))
})

完整可运行代码 #

## Read in necessary libraries, function, and data 
library(shiny)
library(ggplot2)
library(dplyr)
library(scales)

reverselog_trans <- function(base = exp(1)) {
    trans <- function(x) -log(x, base)
    inv <- function(x) base^(-x)
    trans_new(paste0("reverselog-", format(base)), trans, inv, 
              log_breaks(base = base), 
              domain = c(1e-100, Inf))
}

pretend_data <- tibble(data=1:5, estimate = runif(5, min = -1, max = 2), plot = c(1e-50, 2e-35, 5e-1, 1, 50))

# Define UI for application that draws a volcano plot
ui <- fluidPage(
    # Application title
    titlePanel("Pretend Plot"),
        plotOutput("plot", click = "plot_click"),
        tableOutput("data")
 )

# Define server logic required to draw a volcano plot
server <- function(input, output, session) {
    output$plot <- renderPlot({
        ggplot(data = pretend_data, aes(x=estimate, y=plot)) + 
            geom_vline(xintercept=c(-1, 1), linetype=3) +
            geom_hline(yintercept=0.01, linetype=3) +
            geom_point() + 
            scale_y_continuous(trans = reverselog_trans(10))
    }, res = 96)
    
    output$data <- renderTable({
        req(input$plot_click)
        nearPoints(pretend_data, input$plot_click, ytrans = reverselog_trans(10))
    })
}

# Run the application 
shinyApp(ui = ui, server = server)

内容的提问来源于stack exchange，提问作者Madomako