基于Shiny与DT库实现selectInput自定义绘图选中点颜色的求助

Hey there! I see exactly where you went wrong—let's get this working smoothly for you.

The Root Cause #

When you set col = "input$color", you're passing a literal string "input$color" to the points() function, not the actual value of the user's color selection from the selectInput. R doesn't recognize this as a valid color name, which is why you got that error.

Step-by-Step Fix #

1. Place the selectInput logically in your UI
   Let's add it right above the plot in the column(4) section so it's grouped with the element it controls:

   column(4, 
          h3("p5"),
          selectInput("color", "What is your preferred color?", 
                      choices = c("blue", "gold", "green", "pink", "red", "yellow")),
          plotOutput("p5")
          )
   

2. Update the points() call in your server
   Remove the quotes around input$color—this lets Shiny access the reactive value of the user's selected color instead of treating it as plain text:

   points(iris[s, c("Sepal.Length", "Sepal.Width"), drop = F], 
          pch = 19, cex = 1, 
          col = input$color)  # No quotes here!
   

Full Modified Code #

Here's the complete working code with changes highlighted:

library(shiny)
library(DT)
ui <- fluidPage(
  h3("t1"),
  tableOutput("t1"),
  hr(),
  fluidRow(
    column(9, h3("dt1"), dataTableOutput("dt1")),
    column(3, h3("x4"), verbatimTextOutput("x4"))
  ),
  hr(),
  fluidRow(
    column(8, h3("dt2"), dataTableOutput("dt2")),
    column(4, 
           h3("p5"),
           # Added selectInput here for better UI flow
           selectInput("color", "What is your preferred color?", 
                       choices = c("blue", "gold", "green", "pink", "red", "yellow")),
           plotOutput("p5")
           )
  )
)
options(error = function() traceback(2))
server <- function(input, output, session) {
  output$t1 <- renderTable(iris[1:10,], striped = TRUE, hover = TRUE)
  output$dt1 <- renderDataTable(iris, options = list( pageLength = 5))
  output$x4 <- renderPrint({
    s = input$dt1_rows_selected
    if (length(s)) {
      cat('These rows were selected:\n\n')
      cat(s, sep = ', ')
    }
  })
  output$dt2 <- renderDataTable(iris, options = list(pageLength = 5), server = FALSE)
  output$p5 <- renderPlot({
    s <- input$dt2_rows_selected
    plot(iris$Sepal.Length, iris$Sepal.Width)
    if (length(s)) {
      # Removed quotes around input$color to use the reactive value
      points(iris[s, c("Sepal.Length", "Sepal.Width"), drop = F], pch = 19, cex = 1, col = input$color)
    }
  })
}
shinyApp(ui, server)

How It Works Now #

• The selectInput creates a reactive variable input$color that updates automatically when the user picks a new color.
• By using col = input$color (without quotes), Shiny fetches the current value of this input and passes it to points(), so the selected scatter points will always match the user's chosen color.

内容的提问来源于stack exchange，提问作者Chen JG Thomas