library(shiny)

ui <- fluidPage(
  
  h1("Cars Data"),
  
  sidebarLayout(
    sidebarPanel(
      
      fluidRow(
        
        column( width = 12,
        
        uiOutput("bin_selector_ui"),
        
        uiOutput("column_selector_ui"),
        
        "MT Cars Data from R"
        
        )
      )
    ),
    
    
    mainPanel(
      
      plotOutput("histogram_plot"),
      
      plotOutput("scatter_plot")
      
      
    )
    
    
  )
  

  
  
)

server <- function(input, output, session) {
  
  RV = reactiveValues(
    
    data_df = mtcars
    
  )
  
  
  output$bin_selector_ui = renderUI({
    
    sliderInput("bin_selector", "Number of bins:", min = 0, max = 50, value = 30)
    
  })

  
  output$column_selector_ui = renderUI({
    
    selectInput("column_selector", "Choice:", choices = colnames(req(RV$data_df[,-1])))
    
  })
  
  output$histogram_plot = renderPlot({
    
    data_df <- req(RV$data_df)
    
    bins <- req(input$bin_selector)
    
    hist(data_df$mpg, breaks = bins)
    
  })
  
  
  
  output$scatter_plot = renderPlot({
    
    
    data_df <- req(RV$data_df)
    
    selected_column <- req(input$column_selector)
    
    data_df = data_df[, c(selected_column, "mpg")]
    
    plot(data_df)
    
  })
  
}

shinyApp(ui, server)