library(shiny)
library(plotly)

ui <- fluidPage(
  uiOutput("plotly_outputs"),
  radioButtons("switch", "switch", choices = c("horiz", "vert"), selected = "horiz")
)

server <- function(input, output) {
  
  output$plotly_outputs <- renderUI({
    
    if (input$switch == "horiz"){
      ret <- tagList(
        fluidRow(
          column(width = 6, style = "height:450px",
                 plotlyOutput('plotly_blocks', width = '100%', height = '100%')),
          column(width = 6, style = "height:450px",
                 plotlyOutput('plotly_blocks2', width = '100%', height = '100%'))
        )
      )
    } else {
      tagList(
        fluidRow(
          column(width = 12, style = "height:225px",
                 plotlyOutput('plotly_blocks', width = '100%', height = '100%'))),
        fluidRow(
          column(width = 12, style = "height:225px",
                 plotlyOutput('plotly_blocks2', width = '100%', height = '100%')))
      )
    }
  })
  
  output$plotly_blocks <- renderPlotly({
    input$switch
    calc_plot()
  })
  
  output$plotly_blocks2 <- renderPlotly({
    input$switch
    calc_plot()
  })
  
  calc_plot <- reactive({
    input$switch
    
    plot_ly(economics, x = ~date, color = I("black")) %>%
      add_lines(y = ~uempmed) %>%
      add_lines(y = ~psavert, color = I("red"))
  })

}

shinyApp(ui, server)