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library(shiny)
library(datasets)
# Define server logic required to summarize and view the selected
# dataset
function(input, output) {
# By declaring datasetInput as a reactive expression we ensure
# that:
#
# 1) It is only called when the inputs it depends on changes
# 2) The computation and result are shared by all the callers
# (it only executes a single time)
#
datasetInput <- reactive({
switch(input$dataset,
"rock" = rock,
"pressure" = pressure,
"cars" = cars)
})
# The output$caption is computed based on a reactive expression
# that returns input$caption. When the user changes the
# "caption" field:
#
# 1) This function is automatically called to recompute the
# output
# 2) The new caption is pushed back to the browser for
# re-display
#
# Note that because the data-oriented reactive expressions
# below don't depend on input$caption, those expressions are
# NOT called when input$caption changes.
output$caption <- renderText({
input$caption
})
# The output$summary depends on the datasetInput reactive
# expression, so will be re-executed whenever datasetInput is
# invalidated
# (i.e. whenever the input$dataset changes)
output$summary <- renderPrint({
dataset <- datasetInput()
summary(dataset)
})
# The output$view depends on both the databaseInput reactive
# expression and input$obs, so will be re-executed whenever
# input$dataset or input$obs is changed.
output$view <- renderTable({
head(datasetInput(), n = input$obs)
})
}