CODEWITHSUNDEEP
rshiny
Student
Student

Reputation: 35

Detect columns in an uploaded csv in R shiny app

I want to create a shiny app where one can upload a csv file and then select columns of that file. The problem is that after uploading a file, my code fails to update the column names for possible choices. Here is a reproducible example. Thank you!

ui <- fluidPage(  
                    fileInput("file1",
                            "Please choose a csv File",
                            multiple = FALSE,
                            accept   = c("text/csv",
                                         "text/comma-separated-values,text/plain",
                                         ".csv")),
                  
                  
                  div(style="display:inline-block", selectInput('var',
                                                                'Select the first var',
                                                                "") )
)

server <- function( input, output, session ) {
  
  data <- reactive({ 
    
    inFile <- input$file1
    
    req(inFile) 
    
    validate(need(ext == "csv", "Please upload a csv file"))
    
    df =     read.csv(inFile$datapath,
                      header = input$header,
                      sep    = input$sep,
                      quote  = input$quote)
    
    colnames <- names(df)
    
    df
  })
  
  
  output$contents <- renderTable( { 
    updateSelectInput(session, 
                      inputId  = 'var', 
                      label    = 'Select the first var',
                      choices  = colnames) 
  } ) }

shinyApp(ui = ui, server = server)

Upvotes: 1

Views: 966

Answers (1)

Ash
Ash

Reputation: 1513

Some of your reactive expression aren't right, lets split things out to make it easier to follow. In particular use observeEvent to watch the file input.


library(shiny)

ui <- fluidPage(  
    
    fileInput("myfileinput", "Please choose a csv File", multiple = FALSE, accept = c("text/csv", "text/comma-separated-values,text/plain", ".csv")),
    
    selectInput('myselectinput','Select the first var', ""),
    
    tableOutput('mytable')
    
)

server <- function(input, output, session) {
    
    #Reactive to store loaded data
    reactives <- reactiveValues(
        
        mydata = NULL
        
    )
    
    #Observe file being selected
    observeEvent(input$myfileinput, {
        
        #Store loaded data in reactive
        reactives$mydata <- read.csv(file = input$myfileinput$datapath)
        
        #Update select input
        updateSelectInput(session, inputId = 'myselectinput', label = 'Select the first var', choices  = colnames(reactives$mydata))
        
    })
    
    #Data table
    output$mytable <- renderTable({ 
        
        reactives$mydata
        
    })
    
}
    
shinyApp(ui = ui, server = server)

Upvotes: 1

Related Questions