Shiny App：散点图对多个输入做出反应

我正在尝试制作一个闪亮的应用程序，允许用户为散点图的 x 轴和 y 轴选择一个组 ( cut) 和一个变量（即depth、table或）。price下面的 UI 代码可以很好地允许用户进行选择，但是，我在服务器方面遇到了问题。我认为问题在于将 UI 选择过滤到两个数据框中，然后使用rbind()它们来组合它们，但我不知道另一种继续进行的方法。

如何对ggplot()用户对 x 轴和 y 轴的两个选择做出反应？

例子：

library(shiny)
library(tidyverse)

dat <- diamonds %>%
  select(cut,depth,table,price) %>%
  pivot_longer(cols = c('depth','table','price'),
               names_to = 'Variable',
               values_to = 'Value')

ui <- fluidPage(
  selectInput("x_cut", "X-axis Cut", choices = unique(dat$cut)),
  selectInput("x_variable", "X-axis Variable", choices = unique(dat$Variable)),
  selectInput("y_cut", "Y-axis Cut", choices = unique(dat$cut)),
  selectInput("y_variable", "Y-axis Variable", choices = unique(dat$Variable)),
  plotOutput("plot")
)

server <- function(input, output) {
  output$plot <- renderPlot({
    filtered_xdat <- dat %>%
      filter(cut == input$x_cut, Variable == input$x_variable)
    
    filtered_ydat <- dat %>%
      filter(cut == input$y_cut, Variable == input$y_variable)
    
    filtered_dat <- rbind(filtered_xdat, filtered_ydat)
      
    filtered_dat %>%
      ggplot() +
      geom_point(aes(x = input$x_variable,
                     y = input$y_variable)) +
      geom_point()
  })
}

shinyApp(ui, server)

# Warning: Error in geom_point: Problem while setting up geom.
# ℹ Error occurred in the 2nd layer.
# Caused by error in `compute_geom_1()`:
#   ! `geom_point()` requires the following missing aesthetics: x and y

我已经尝试过这个：

server <- function(input, output) {
  output$plot <- renderPlot({

    filtered_xdat <- dat %>%
      filter(cut == input$x_cut,
             xVariable == input$x_variable) %>%
      as.data.frame()

    filtered_ydat <- dat %>%
      filter(cut == input$y_cut,
             yVariable == input$y_variable) %>%
      as.data.frame()

    ggplot() +
      geom_point(aes(x = filtered_xdat$xVariable, y = filtered_ydat$yVariable)) +
      theme_minimal()
  })
}

# Warning: Error in filter: ℹ In argument: `xVariable == input$x_variable`.
# Caused by error:
#   ! object 'xVariable' not found

还有这个：

server <- function(input, output) {
  output$plot <- renderPlot({

    filtered_dat <- dat %>%
      filter(cut %in% c(input$x_cut, input$y_cut),
             Variable %in% c(input$x_variable, input$y_variable))
    
    ggplot(data = filtered_dat, aes(x = !!sym(input$x_variable), y = !!sym(input$y_variable))) +
      geom_point() +
      theme_minimal()
  })
}

# Warning: Error in geom_point: Problem while computing aesthetics.
# ℹ Error occurred in the 1st layer.
# Caused by error in `FUN()`:
#   ! object 'depth' not found