Load plot upon launching Shiny app about shiny HOT 1 OPEN

library(shiny)

ui <- fluidPage(
  plotOutput("plot_ui"),
  actionButton("ab","press to change")
)

server <- function(input, output, session) {
  
  output$plot_ui <- renderPlot({
   
    if (isTruthy(input$ab)){
      plot(iris$Sepal.Length,iris$Sepal.Width)
      title(paste0("Chosen: iris - ", input$ab))
    } else{
       plot(cars$speed,cars$dist)
      title("Default: cars")
    }

  })
}

shinyApp(ui, server)