In Shiny, how to see which action happen later? - r

Question

In my app, the user can upload their file as the input data (using file upload widget). If they don't have their data, I provide some demo data (user can choose demo data by clicking actionButton).
How do I make a variable = the upload OR the demo, whichever is later? Any help is appreciated.
server.R
library(shiny)
DemoData = data.frame('Col.1'=c('Demo','Demo'),
'Col.2'=c('Data','Data'))
shinyServer(function(input, output) {
# option 1: use demo data
getDemo = eventReactive(input$Demo,{
DemoData
})
# option 2: user upload data
getUpload = reactive({
inFile = input$file
if (is.null(inFile)) return(NULL)
read.csv(inFile$datapath)
})
# need getData() to be option 1 or 2, whichever happened later
# should respond to multiple times of changing between option 1 and 2
getData = # ??? getDemo() or getUpload(), whichever is later
# show the data
output$InputData = renderDataTable({
as.data.frame( getData() )
})
})
ui.R
library(shiny)
shinyUI(fluidPage(
titlePanel(h2("Hello Shiny")),
sidebarLayout(
sidebarPanel(
fileInput('file',
'Choose CSV File (two columns: Town and State)',
accept=c('text/csv',
'text/comma-separated-values,text/plain',
'.csv')
),
actionButton('Demo', 'Use Demo Data')
),
mainPanel(
tabsetPanel(
tabPanel(title=h4('Data'),
column(5, tags$h3('Input Data'), dataTableOutput('InputData'))
)
)
)
)
))
UserData.R (maybe make it easier for you to test)
getwd()
setwe()
UserData = data.frame('Col.1'=c('User','User'),
'Col.2'=c('Data','Data'))
write.csv(UserData, file="UserData.csv", row.names=FALSE)

Answer 1

You can use observers, one to watch the demo button and one to watch for file uploads. Both update the same reactive data, so you see the effect of whichever happened last.
library(shiny)
DemoData <- data.frame('Col.1'=1:10,
'Col.2'=rnorm(10))
shinyApp(
shinyUI(fluidPage(
titlePanel(h2("Hello Shiny")),
sidebarLayout(
sidebarPanel(
fileInput('file',
'Choose CSV File (two columns: Town and State)',
accept=c('text/csv',
'text/comma-separated-values,text/plain',
'.csv')
),
actionButton('Demo', 'Use Demo Data')
),
mainPanel(
tabsetPanel(
tabPanel(title=h4('Data'),
column(5, tags$h3('Input Data'), tableOutput('InputData'))
)
)
)
)
)),
shinyServer(function(input, output) {
values <- reactiveValues() # store values to be changed by observers
values$data <- data.frame()
## Observer for uploaded file
observe({
inFile = input$file
if (is.null(inFile)) return(NULL)
values$data <- read.csv(inFile$datapath)
})
## Observer for demo data button
observe({
if (input$Demo > 0) # otherwise demo data shows on startup
values$data <- DemoData
})
## show the data
output$InputData = renderTable({
values$data
})
})
)