How to import a csv, makes it reactive and create plots - r

Question

I'm trying to create a shiny app that imports different csv's and create plots using for example the package pROC.
library(shiny)
library(datasets)
ui <- shinyUI(fluidPage(
titlePanel("Column Plot"),
tabsetPanel(
tabPanel("Upload File",
titlePanel("Uploading Files"),
sidebarLayout(
sidebarPanel(
fileInput('file1', 'Choose CSV File',
accept=c('text/csv',
'text/comma-separated-values,text/plain',
'.csv')),
tags$br(),
checkboxInput('header', 'Header', TRUE),
radioButtons('sep', 'Separator',
c(Comma=',',
Semicolon=';',
Tab='\t'),
','),
radioButtons('quote', 'Quote',
c(None='',
'Double Quote'='"',
'Single Quote'="'"),
'"')
),
mainPanel(
tableOutput('contents')
)
)
),
tabPanel("First Type",
pageWithSidebar(
headerPanel('My First Plot'),
sidebarPanel(
selectInput('xcol', 'X Variable', ""),
selectInput('ycol', 'Y Variable', "", selected = "")
),
mainPanel(
plotOutput('MyPlot')
)
)
)
)
)
)
server <- shinyServer(function(input, output, session) {
data <- reactive({
req(input$file1)
inFile <- input$file1
df <- read.csv(inFile$datapath, header = input$header, sep = input$sep,
quote = input$quote)
updateSelectInput(session, inputId = 'xcol', label = 'X Variable',
choices = names(df), selected = names(df))
updateSelectInput(session, inputId = 'ycol', label = 'Y Variable',
choices = names(df), selected = names(df)[2])
return(df)
})
output$contents <- renderTable({
data()
})
output$MyPlot <- renderPlot({
x <- data()[, c(input$xcol, input$ycol)]
pROC::roc(input$xcol,input$ycol)
})
})
shinyApp(ui, server)
I have tried to use different codes available in blogs, however, I did not find anything similar. It is possible to reproduce simple plots, like histograms but when I try to import the package proc for example there are always errors associated in this case: 'response' must have two levels

Answer 1

The input variable that you get in the server lists the column names in xcol and ycol. pROC's roc function expects the data itself, which you need to get from your data like for instance:
pROC::roc(x[[input$xcol]], x[[input$ycol]])