Other User Interface Options

• tabsetPanel() - make multiple different output views (i.e. a plot in one tab, a data table in another)
• helpText() - create additional text to help users navigate your applet
• submitButton() - only update outputs when this button is clicked
• conditionalPanel() - only show certain UI options when conditions are met (i.e. if a certain tab is open, or a certain input is selected)

resource

Getting the shiny app to react: server

• the server function connects inputs to outputs
• render functions create outputs of different types

server  <-  function(input, output) {
  # make output objects from inputs  
  
  output$hist <- renderPlot({
    # code for plot
  
  })
}

Render functions

• renderDataTable() - outputs an interactive, sortable data table
• renderPlot() - output an R plot
• renderPrint() - output text from print() in R
• renderTable() - output an HTML table
• renderText() - output text from R
• renderUI() - output a custom part of the user interface
• renderImage() - print an image to the page
• htmlOutput() - output html elements

Example server function

server <- function(input, output) {
    output$hist <- renderPlot({
        dist <- rnorm(n = input$num)
        gg <- data.frame(dist) %>% 
          ggplot(aes(x = dist)) + geom_histogram(binwidth = 0.25) +
          xlim(c(-10,10))
        print(gg)
    })
}

Note the use of curly brackets { } in renderPlot.

The last statement in the code block must be the plot.

Your Turn

For the 01_Hello app:

• expand on the server functionality to make the plot react to the input

An example

runApp("02_Reactivity", display.mode = "showcase")

Your Turn

Using your own data or the NYC crime data provided, create a simple Shiny app. Use the NYC_Emergency app as a starting point.

runApp("03_NYC_Emergency")

• Ideas:
  • Plot some aspect of the data with color based on another aspect of the data
  • Use subset() and checkboxInput() to plot user-selected subsets
  • Use tabsetPanel() to display different tables/plots
  • Extra Challenging: Can you make a map of NYC crime by location?