Upload csv and read it as h2o object in a shiny app

Question

Im trying to upload a csv file to a shiny app as a h2o object based on this process but I get Warning: Error in .key.validate: key must match the regular expression '^[a-zA-Z_][a-zA-Z0-9_.]*$': 0_sid_b018_4. Im not sure if there is a problem with path reading or the table

#install h2o first
if ("package:h2o" %in% search()) { detach("package:h2o", unload=TRUE) }
if ("h2o" %in% rownames(installed.packages())) { remove.packages("h2o") }


if (! ("methods" %in% rownames(installed.packages()))) { install.packages("methods") }
if (! ("statmod" %in% rownames(installed.packages()))) { install.packages("statmod") }
if (! ("stats" %in% rownames(installed.packages()))) { install.packages("stats") }
if (! ("graphics" %in% rownames(installed.packages()))) { install.packages("graphics") }
if (! ("RCurl" %in% rownames(installed.packages()))) { install.packages("RCurl") }
if (! ("jsonlite" %in% rownames(installed.packages()))) { install.packages("jsonlite") }
if (! ("tools" %in% rownames(installed.packages()))) { install.packages("tools") }
if (! ("utils" %in% rownames(installed.packages()))) { install.packages("utils") }


install.packages("h2o", type = "source", repos = (c("http://h2o-release.s3.amazonaws.com/h2o/latest_stable_R")))
library(h2o)
h2o.init()

#app
library(shiny)
library(h2o)
h2o.init()

# Define UI for data upload app ----
ui <- fluidPage(
  
  # App title ----
  titlePanel("Uploading Files"),
  
  # Sidebar layout with input and output definitions ----
  sidebarLayout(
    
    # Sidebar panel for inputs ----
    sidebarPanel(
      # Input: Select a file ----
      fileInput("file1", "Choose CSV File",
                multiple = FALSE,
                accept = c("text/csv",
                           "text/comma-separated-values,text/plain",".xlsx",
                           ".csv")),
      
      # Horizontal line ----
      tags$hr(),
      
      # Input: Checkbox if file has header ----
      checkboxInput("header", "Header", TRUE),
      
      # Input: Select separator ----
      radioButtons("sep", "Separator",
                   choices = c(Comma = ",",
                               Semicolon = ";",
                               Tab = "\t"),
                   selected = ","),
      
      # Input: Select quotes ----
      radioButtons("quote", "Quote",
                   choices = c(None = "",
                               "Double Quote" = '"',
                               "Single Quote" = "'"),
                   selected = '"'),
      
      # Horizontal line ----
      tags$hr(),
      
      # Input: Select number of rows to display ----
      radioButtons("disp", "Display",
                   choices = c(Head = "head",
                               All = "all"),
                   selected = "head")
      
    ),
    
    # Main panel for displaying outputs ----
    mainPanel(
      
      # Output: Data file ----
      tableOutput("contents")
      
    )
    
  )
)

# Define server logic to read selected file ----
server <- function(input, output) {
  file_info <- reactive({
    # input$file1 will be NULL initially. After the user selects
    # and uploads a file, head of that data file by default,
    # or all rows if selected, will be shown.
    
    req(input$file1)
   
      # when reading semicolon separated files,
      # having a comma separator causes `read.csv` to error
      tryCatch(
        {
          path <- input$file1$datapath
          data <- h2o.uploadFile(path = path)
          df <- read.csv(data,
                         header = input$header,
                         sep = input$sep,
                         quote = input$quote)
        },
        error = function(e) {
          # return a safeError if a parsing error occurs
          stop(safeError(e))
        }
      )
      
      if(input$disp == "head") {
        return(head(df))
      }
      else {
        return(df)
      }
    
    
  })
  output$contents <- renderTable({
    
    file_info()
  })
  
}

# Create Shiny app ----
shinyApp(ui, server)

Answer 1

I see there 2 issues:

• H2O-3 requires its internal keys to start with a letter. The internal key is derived from the file name. When shiny uploads the file it renames it and in this case the file was named 0.csv. To workaround this you can specify destination_frame, e.g.:

data <- h2o.uploadFile(path = path, destination_frame = paste0("file_", digest::digest(path)))

• The other issue is reading the csv. You use read.csv(data) where data is an H2OFrame, this will not work. You should use as.data.frame(data) or read.csv(path, ...).