美学必须是长度1或与数据（1）相同：颜色

Question

I am trying to plot a graph that will change based on selected inputs. Moreover, the data in the graph should be categorized by state. The dataset that I am using is midwest which is from ggplot2 . For some reason, the color which should be based off of the state from the midwest dataset is not working. I get the error when I try to use color = state or color = prof_poverty$state . Aesthetics must be either length 1 or the same as the data (1): colour . There should be 5 different colors since there are 5 different states.

This is my code:

UI

library(shiny)
library(dplyr)
library(ggplot2)

prof_poverty <- midwest %>%
    select(state, county, percprof, percadultpoverty, percpovertyknown, percbelowpoverty, percadultpoverty, percelderlypoverty, percchildbelowpovert)

ui <- fluidPage(
   pageWithSidebar(
       headerPanel('Poverty compared with number of professors'),
       sidebarPanel(
           selectInput('xcol', 'X variable', names(prof_poverty)[3:8]),
           selectInput('ycol', 'Y variable', names(prof_poverty)[3:8]),
           selected = names(prof_poverty)[[2]]
       ),
       mainPanel(
           plotOutput('poverty')
       )
   )
)

SERVER

# Define server that renders a map and a table
server <- function(input, output){
    # Combine the selected variables into a new data frame
    selectedData <- reactive({
        prof_poverty[input$xcol, input$ycol]
    })

    output$poverty <- renderPlot ({
    ggplot(data = selectedData(), aes(x = input$xcol, y = input$ycol)) +
        geom_point(aes(color = prof_poverty$state)) })
}
# sRun the application 
shinyApp(ui = ui, server = server)

Answer 1

Just changing the data used in the ggplot call to prof_poverty and using aes_string should work. (although there are more modern ways to deal with this)

The way you have subset the data in your reactive selectedData hasn't worked and the use of the full vector of states in the colour aesthetic is triggering the error.

Given the renderPlot function is reactive, you don't really need a reactive data object selectedData created before this anyway.

server <- function(input, output){

  output$poverty <- renderPlot ({
    ggplot(data = prof_poverty, aes_string(x = input$xcol, y = input$ycol)) +
      geom_point(aes(color = prof_poverty$state)) })
}
# Run the application 
shinyApp(ui = ui, server = server)