Running scripts on uploaded csv file in shiny - r

Question

I'm trying to build an application that takes a csv file from the user, uploads it, then the user fill some text boxes that will fill specific columns in the data frame later on, clicks a button 'GO', some scripts run in the background and we have a data frame ready for download. The thing is the whole reactive architecture makes it difficult to set up a step by step algorithm. Could you help me with setting up the framework for doing that? Ideally it would look like follows
shinyUI(fluidPage(
titlePanel("Uploading Files"),
fileInput('file1', 'Choose file to upload',
accept = c('text/csv',
'text/comma-separated-values',
'text/tab-separated-values',
'text/plain','.csv','.tsv')),
dateInput('date',"Select when the file was uploaded",
value = NULL,
format = 'yyyy-mm-dd'),
textInput('text1','Type what will be in column 6'),
textInput('text2','Type what will be in column 7'),
actionButton('go','go'),
tableOutput('readytable')
And now having that front i would like to: 1. Load the dataframe from csv of the user 2. Wait for the user to fill other input boxes 3. After clicking 'go' run bunch of functions on the data frame with the inputs that the user have inserted as for example df$column6 <- input$text1 and after that i'm left with a data frame that is ready to be written as a csv file once again. Thanks in advance for any links/suggestions

Answer 1

You can use reactive variables to control reactivity on shiny. Here is an example for your problem. Please note that the download button doesn't works on the RStudio viewer, so launch the app in a browser if you want to use the download button.
library(shiny)
runApp(list(
ui = shinyUI(pageWithSidebar(
headerPanel('Uploading Files'),
sidebarPanel(
fileInput('file1', 'Choose file to upload',
accept = c('text/csv',
'text/comma-separated-values',
'text/tab-separated-values',
'text/plain','.csv','.tsv')),
uiOutput('buttonsUI'), br(),
uiOutput('downloadUI')
),
mainPanel(
tableOutput('readytable')
)
)),
server = shinyServer(function(input, output) {
# variables to control the sequence of processes
controlVar <- reactiveValues(fileReady = FALSE, tableReady = FALSE)
# to keep the data upload
dat <- NULL
# handle the file reading
observeEvent(input$file1, {
controlVar$fileReady <- FALSE
if (is.null(input$file1))
return()
inFile <- input$file1
dat <<- read.csv(inFile$datapath)
if(!is.data.frame(dat))
return()
controlVar$fileReady <- TRUE
})
# show buttons only when file is uploaded
output$buttonsUI <- renderUI({
if (controlVar$fileReady)
div(
dateInput('date','Select when the file was uploaded',
value = NULL,
format = 'yyyy-mm-dd'),
textInput('text1','Type what will be in column 6'),
textInput('text2','Type what will be in column 7'),
actionButton('go','go')
)
})
# show a download button only if data is ready
output$downloadUI <- renderUI({
if (controlVar$tableReady)
downloadButton('downloadData', 'Download')
})
# add columns to dat and run some script on it
observeEvent(input$go, {
controlVar$tableReady <- FALSE
if (!is.null(input$text1))
dat$column6 <<- input$text1
if (!is.null(input$text2))
dat$column7 <<- input$text2
# simulate running a cool script on dat
Sys.sleep(2)
controlVar$tableReady <- TRUE
})
# render table after uploading file or running the script
output$readytable <- renderTable({
input$go
if (controlVar$fileReady || controlVar$tableReady)
dat
})
# handle the download button
output$downloadData <- downloadHandler(
filename = function() { 'newData.csv' },
content = function(file) {
write.csv(dat, file)
}
)
})
))