Shiny Dashboard Building Blocks - Reference Summary

This handout summarizes key Shiny concepts, functions, and patterns you can use when building interactive dashboards.

Shiny App Structure

Every Shiny app has two main components:

Component	Purpose	Location
ui	User Interface - controls layout and inputs	Top-level ui <- ...
server	Logic - computations, data processing, outputs	Inside server <- function(input, output) { ... }

The two are linked using shared inputId and outputId values.

Inputs and Outputs

Input Widgets

Type	Function	When to Use
Dropdown	selectInput()	For long lists (e.g., Province selection)
Checkboxes	checkboxGroupInput()	For multiple selections
Radio Buttons	radioButtons()	For short lists
Single Checkbox	checkboxInput()	For TRUE/FALSE toggles
Slider	sliderInput()	For numeric ranges
Date	dateInput() / dateRangeInput()	For date selection

Each input requires:

inputId = "input_name", label = "Display Text", choices = c(...)

The current value is accessed using input$input_name inside the server.

Output Types

Output	Render Function (Server)	UI Function
Text	renderText()	textOutput()
Table (static)	renderTable()	tableOutput()
Table (interactive)	renderDT()	DTOutput()
Plot (static)	renderPlot()	plotOutput()
Plot (interactive)	renderPlotly()	plotlyOutput()
Map	renderLeaflet()	leafletOutput()
Dynamic UI	renderUI()	uiOutput()

Key rule: every output has one render*() function (server) and one *Output() function (UI), linked by the same ID.

Reactivity

Reactivity allows the app to update automatically when inputs change.

• Use reactive({ ... }) to create filtered or computed datasets that update when inputs change.

• Use render*() functions to update outputs.

Example reactive filter:

province_data <- reactive({ req(input$province_select != "")

app_data %>% filter(organisation_unit == input$province_select) })

Layout Tools

• page_sidebar(): main layout with sidebar + content

• layout_sidebar(): floating sidebar inside a card

• card(): container for plots/tables

• value_box(): summary KPIs

• layout_columns(): arrange elements horizontally

• layout_column_wrap(): responsive wrapping of multiple boxes

Exaple layout:

layout_columns(   
  value_box(title = "Cases", value = textOutput("total_cases")),  
  value_box(title = "Tests", value = textOutput("total_tests")) 
  )

Conditional UI Elements

• Use renderUI() + uiOutput() to dynamically generate inputs or outputs.

• Use validate() and need() to display user prompts when required inputs are missing.

output$tpr_checkbox_ui <- renderUI({
  if (all(c("malaria_cases", "malaria_tests") %in% input$series_select)) {
    checkboxInput("include_tpr", "Calculate TPR", value = FALSE)
  }
})

Theming and Styling

• Use bslib::bs_theme() to apply consistent color schemes and fonts.

• Use input_dark_mode() to enable light/dark toggle.

• Use Bootstrap icons via bsicons::bs_icon() for value boxes and UI elements.

theme = bs_theme(version = 5, bootswatch = "minty")

Data Export

Allow users to download tables using downloadHandler().

Example:

output$download_data <- downloadHandler(
  filename = function() { "summary.csv" },
  content = function(file) { write.csv(summary_data(), file) }
)

Useful Resources

• Shiny Documentation

• Mastering Shiny Book

• bslib Theming Guide