R Shiny: Some reactivity by example

Start R from the directory containing ui.r and server.r, import the shiny library and start the (development) server using runApp().

server.r

function(input, output) {

    rv <- reactiveValues()

    # Only modify and output reactive input

    output$numOut1 <- renderText({

        input$n+10

    })

    

    # Modify, reassign and output reactive input.

    output$numOut2 <- renderText({

        rv$a <- input$n+20

    })

    

    # Use modified reactive input, modify and output.

    output$num1 <- renderText({

        rv$s <- rv$a+runif(1)

    })

    

    # Assign reactive input locally, modify locally, print.

    output$num2 <- renderText({

        k <- input$n

        paste(as.character(runif(1)), "here", k-10)

    })

    

    # Use reactive value from another reactive function,

    # modify and print.

    output$let <- renderText({

        paste(as.character(rv$s), sample(letters, 1), sep="")

    })

}

ui.r

fluidPage(

    numericInput(inputId="n", "Shiny Reactivity Example", value=25),

    textOutput(outputId="numOut1"),

    

    textOutput(outputId="numOut2"),

    

    textOutput(outputId="num1"),

    textOutput(outputId="num2"),

    textOutput(outputId="let")

)