How can I display multiple.xpt files in R shiny and filter them based on their columns?

The reason the app starts to fail when multiple files are uploaded, is because inFile$datapath stops being a single value. Now it contains multiple datapaths corresponding to each file.

Here is an example app that lets the user upload multiple .xpt files and select which file to display on the table.

library(shiny)
library(haven)
library(stringr)

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      fileInput("file1", "Choose CSV File",
        multiple = TRUE,
        accept = c(
          "text/csv",
          "text/comma-separated-values,text/plain",
          ".csv", ".xpt"
        )
      ),
      tags$hr(),
      checkboxInput("header", "Header", TRUE),
      uiOutput("files_available")
    ),
    mainPanel(
      tableOutput("contents")
    )
  )
)

server <- function(input, output) {
  output$files_available <- renderUI({
    req(input$file1)
    selectInput("name", str_to_title("select which file to show"), choices = input$file1$name)
  })

  df <- reactive({
    req(input$name)
    read_xpt(input$file1$datapath[[which(input$file1$name == input$name)]])
  })

  output$contents <- renderTable({
    df()
  })
}

shinyApp(ui, server)

Edit: The app with filter:

library(shiny)
library(haven)
library(stringr)
library(shinyWidgets)
library(tidyverse)

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      fileInput("file1", "Choose CSV File",
        multiple = TRUE,
        accept = c(
          "text/csv",
          "text/comma-separated-values,text/plain",
          ".csv", ".xpt"
        )
      ),
      tags$hr(),
      checkboxInput("header", "Header", TRUE),
      uiOutput("files_available"),
      uiOutput("filters")
    ),
    mainPanel(
      uiOutput("tables")
    )
  )
)

server <- function(input, output) {
  nms <- reactiveVal(NULL)

  suffixes <- c("STUDYID", "DOMAIN", "VALUE")

  df <- reactive({
    req(input$file1)
    input$file1$datapath %>%
      map(~ read_xpt(.x))
  })

  # for debugging
  observe({
    print(df())
    # print(nms())
    # print(map(names(input), ~input[[.x]]))
  })


  observeEvent(df(), {
    nms(map(df(), names))
  })

  output$filters <- renderUI({
    req(df())
    inpts <- tagList(
      numericInput("STUDYID", "STUDYID", value = NA),
      textInput("DOMAIN", "DOMAIN", value = ""),
      numericInput("VALUE", "VALUE", value = NA)
    )
  })

  output$tables <- renderUI({
    req(df())
    map(1:length(df()), ~ tableOutput(str_c("table", .x)))
  })

  observeEvent(c(input$STUDYID, input$DOMAIN, input$VALUE), {
    df <- df()
    # df contains multiple dataframes so we need to loop through each of them to create the render functions
    walk(1:length(df), ~ {
      output[[str_c("table", .x)]] <<- renderTable({
        cur_df <- df[[.x]]
        nms <- nms()[[.x]]
        nms <- map(suffixes, ~ str_subset(nms, .)) # to order the correct column names with the required input. Warning, if more than one name matches the suffix is not tested
        # first we look if the input is character type and force a NA value on it, if it's not we just look for NA.
        # If the input is not NA (meaning that is has a value inserted by the user), then filter the table by that value.
        walk2(nms, suffixes, ~ {
          if (class(input[[.y]]) == "character") {
            if (input[[.y]] == "") {
              input_value <- NA
            } else {
              input_value <- input[[.y]]
            }
          } else {
            input_value <- input[[.y]]
          } # empty textInput's show has an empty string value instead of NA
          print(input_value)
          if (!is.na(input_value)) {
            cur_df <<- cur_df %>% filter(.data[[.x]] == input[[.y]])
          }
        })
        cur_df
      })
    })
  })
}

shinyApp(ui, server)