server.R

diabetesRisk <- function(glucose) glucose / 200

shinyServer(
  function(input, output) {
    output$inputValue <- renderPrint({input$glucose})
    output$prediction <- renderPrint({diabetesRisk(input$glucose)})
  }
)

ui.R

shinyUI(
  pageWithSidebar(
    # Application title
    headerPanel("Diabetes prediction"),
    
    sidebarPanel(
      numericInput('glucose', 'Glucose mg/dl', 90, min=50, max=200, step = 5),
      submitButton('Submit')
    ),
    mainPanel(
      h3('Results of prediction'),
      h4('You entered'),
      verbatimTextOutput('inputValue'),
      h4('Which resulted in a prediction of '),
      verbatimTextOutput("prediction")
    )
  )
)