R Shiny. Change colors on a scatterplot based on selected input categorical variable

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I am trying to make a shiny app that will allow to color the points of the scatterplot based on the selected categorical variables.

library(shiny)
data<-data.frame(iris)

ui <- navbarPage("Summary",
                 tabsetPanel(
                   tabPanel("Graph", fluid=T,
                            fluidPage(
                              sidebarPanel(selectInput(inputId = "varColor",
                                                       label = "Color",
                                                       choices = c("Species", "Other_Category"),
                                                       selected = "Species")),
                              mainPanel(plotOutput(outputId = "plot"))
                            )
                   )
                 )
)

server <- function(input, output) {
p<-reactive({ggplot(data,
       aes(y = Sepal.Length, x = Petal.Length))+
    # This Part needs help
  geom_point(aes( input$varColor)) })


output$plot <- renderPlot({
  p()
  
  })
}

shinyApp(ui, server)

I think that now, the program reads the color selection from the input as a string, instead of taking it as category. Thank you for help.

shiny r
1 Answers

The issue is that input$colorVar is simply a character. Hence, ggplot2 will treat this character value as the one and only category. Hence, you end up with one color.

To tell ggplot2 that it should color the plot according to the data column whose named is stored in input$colorVar you could make use of the so called .data pronoun provided by the rlang package, i.e. do aes(color = .data[[input$varColor]]):

library(shiny)
library(ggplot2)

data <- data.frame(iris)

ui <- navbarPage(
  "Summary",
  tabsetPanel(
    tabPanel("Graph",
      fluid = T,
      fluidPage(
        sidebarPanel(selectInput(
          inputId = "varColor",
          label = "Color",
          choices = c("Species", "Other_Category"),
          selected = "Species"
        )),
        mainPanel(plotOutput(outputId = "plot"))
      )
    )
  )
)
#> Warning: Navigation containers expect a collection of `bslib::nav()`/
#> `shiny::tabPanel()`s and/or `bslib::nav_menu()`/`shiny::navbarMenu()`s. Consider
#> using `header` or `footer` if you wish to place content above (or below) every
#> panel's contents.

server <- function(input, output) {
  p <- reactive({
    ggplot(
      data,
      aes(y = Sepal.Length, x = Petal.Length)
    ) +
      # This Part needs help
      geom_point(aes(color = .data[[input$varColor]]))
  })


  output$plot <- renderPlot({
    p()
  })
}

shinyApp(ui, server)
#> 
#> Listening on http://127.0.0.1:3070

user_129938610
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