Reading in a file in R Shiny

Question

So I am building an app in R shiny that requires the user to upload a .csv file. Once read in by R shiny, I am unsure how to actually manipulate that object to use. The general code syntax is the following:

The UI file:

#ui.R
# Define UI for random distribution application 
shinyUI(fluidPage(

  # Application title
  titlePanel("ORR Simulator"),

  # Sidebar with controls to select the random distribution type
  # and number of observations to generate. Note the use of the
  # br() element to introduce extra vertical spacing
  sidebarLayout(
    sidebarPanel(
          fileInput('file1', 'Select the XXX.csv file',
                accept=c('text/csv','text/comma-separated-values,text/plain','.csv')),
      tags$hr(),
          fileInput('file2', 'Select the YYY.csv file',
                accept=c('text/csv','text/comma-separated-values,text/plain','.csv')),
      tags$hr(),
     numericInput("S", "Number of simulations to run:", 100),

       mainPanel(
plotOutput("plot")
    )
  )
))

The server file:

#server.R
library(shiny)

shinyServer(function(input, output) {

text1 <- renderText({input$file1})
text2 <- renderText({input$file2})

file1 = read.csv(text1)
file2 = read.csv(text2)

output$plot <- renderPlot({

plot(file1[,1],file2[,2])

})


})

And so I would have expected text1 and text2 to hold strings containing the file path to where the files are but that does not seem to be the case. Ultimatley I just want to be able to read in two data sets and from there be able to do analysis to output based on those two data sets.

Of course using renderText might be the wrong idea as well so any suggestions on how to do this better is greatly appreciated.

Answer 1

There is a good example here http://shiny.rstudio.com/gallery/file-upload.html. But for completeness, I've included the working answer below. The key point is that you should reference the file using file$datapath, and also to check if input is NULL (when user hasn't uploaded a file yet).

server.R

#server.R
library(shiny)

shinyServer(function(input, output) {

    observe({
        file1 = input$file1
        file2 = input$file2
        if (is.null(file1) || is.null(file2)) {
            return(NULL)
        }
        data1 = read.csv(file1$datapath)
        data2 = read.csv(file2$datapath)
        output$plot <- renderPlot({
            plot(data1[,1],data2[,2])
        })
    })

})

ui.R

library(shiny)

#ui.R
# Define UI for random distribution application 
shinyUI(fluidPage(

    # Application title
    titlePanel("ORR Simulator"),

    # Sidebar with controls to select the random distribution type
    # and number of observations to generate. Note the use of the
    # br() element to introduce extra vertical spacing
    sidebarLayout(
        sidebarPanel(
            fileInput('file1', 'Select the XXX.csv file',
                      accept=c('text/csv','text/comma-separated-values,text/plain','.csv')),
            tags$hr(),
            fileInput('file2', 'Select the YYY.csv file',
                      accept=c('text/csv','text/comma-separated-values,text/plain','.csv')),
            tags$hr(),
            numericInput("S", "Number of simulations to run:", 100)
        ),
        mainPanel(
            plotOutput("plot")
        )
    ))
)