Change Colors of ggplot based on Radio Button Selection (R Shiny)

Question

I am trying to have a ggplot graph updated each time you select a different radio button, but it's not working quite right. What I want to have happen is the selection of the radio button change the color on the graph. There are three separate categories, so ideally, if the first button was selected: Category 1 would be green (or whatever color I choose) and Categories 2 and 3 would be the same colors, but different from 1. Here is my code:

# Define UI for application
ui = fluidPage(
  navbarPage("Example Problem",
            
             tabPanel("Example",
                      tabname="example",
                      icon=icon("thumbs-up"),
                      prettyRadioButtons(inputId = "rb", 
                                         label = "Make a selection:",
                                         c("3","4","5"),
                                         animation = "pulse",
                                         inline=TRUE),               
                      plotOutput("plot_example")
             )
                      ))


# Define server logic 
server <- function(input, output) {

  
  output$plot_example=renderPlot({
    df=as.data.frame(table(mtcars$carb,mtcars$gear))
    df$C3=ifelse(df$Var2==3,1,0)
    df$C4=ifelse(df$Var2==4,1,0)
    df$C5=ifelse(df$Var2==5,1,0)

    
    switch(input$rb,
           
           "3"=ggplot(data=df, aes(x=Var1, y=Freq, fill=factor(C3))) + geom_bar(stat="identity", position=position_dodge())+
             scale_fill_brewer(palette="Paired")+geom_text(aes(label=Freq), position=position_dodge(width=0.9), vjust=-0.25),
           "4"=ggplot(data=df, aes(x=Var1, y=Freq, fill=factor(C4))) + geom_bar(stat="identity", position=position_dodge())+
             scale_fill_brewer(palette="Paired")+geom_text(aes(label=Freq), position=position_dodge(width=0.9), vjust=-0.25),
           "5"=ggplot(data=df, aes(x=Var1, y=Freq, fill=factor(C5))) + geom_bar(stat="identity", position=position_dodge())+
             scale_fill_brewer(palette="Paired")+geom_text(aes(label=Freq), position=position_dodge(width=0.9), vjust=-0.25))
  })
  
  
}

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

The bar chart moves around with each selection of the radio button and seems to group the two categories that are not selected. How do I keep the bar charts static but the color to react appropriately to the radio button selection?

Is there a better way I can go about doing this? Any help would be appreciated!

Answer 1

I have ignored your columns C1 , C2 and C3 and used Var2 as the fill variable. Assuming that, is this what you are after?

server <- function(input, output) {
  
  output$plot_example = renderPlot({
    df = as.data.frame(table(mtcars$carb, mtcars$gear))
    
    colors <- switch(
      input$rb,
      "3" = c("green", "grey", "grey"),
      "4" = c("grey", "green", "grey"),
      "5" = c("grey", "grey", "green")
    )

    ggplot(data = df, aes(x = Var1, y = Freq, fill = factor(Var2))) +
      geom_bar(stat = "identity", position = position_dodge(), colour = "black") +
      scale_fill_manual(values = colors) +
      geom_text(aes(label = Freq),
                position = position_dodge(width = 0.9),
                vjust = -0.25)
  })
}

You could make the assignment of colors to scale_fill_manual more robust in case you have more variation; this is just the simplest way to go.