Demo example for reactiveVal() with observeEvent() - Create dependency on actionButton - Subset data on click of actionButton and display in datatable

App.R

# Demo example for reactiveVal with observeEvent()
# Create dependency on a button to reflect user input changes to the rendered output 
library(shiny) # for Shiny components
library(dplyr) # for piping

my = mtcars %>% 
  mutate(cyl = as.factor(cyl))

ui <- fluidPage(
  h4("Demo of using reactiveVal() along with observeEvent() in R Shiny to subset data and display on click of action Button"),
  hr(),
  # SliderInput
  sliderInput(inputId = "miles", 
              label ="Select miles per gallon range", 
              dragRange = TRUE, 
              min= min(my$mpg),
              max = max(my$mpg),
              value = c(15, 25)
  ),
  
  #RadioButton
  radioButtons(inputId = "cyl" , 
               label ="Select the cylinder #" , 
               choices =levels((my$cyl)) , 
               selected = 4, 
               inline = TRUE),
  
  
  # Action button
  actionButton(inputId ="show" ,label = "Show Data"),
  
  # Data Table
  tableOutput("table")
  
  # Plot
  
)

server <- function(input, output, session) {
  
  # initialize the reactive data object using reactiveVal
  sub = reactiveVal()
  
  
  # filtering / subsetting within the reactive function on click of action Button
  observeEvent(eventExpr = input$show,
               # update the data object based on use inputs
               sub(dplyr::filter(my, 
                                 cyl==input$cyl,
                                 mpg>=input$miles[1] & mpg<=input$miles[2])),
               ignoreNULL = FALSE # so as to get the datatable displayed with initial selections
  )
    
    # display the subset data
  output$table <- renderTable({
    sub()
    
  })
  
}

shinyApp(ui, server)