R Shiny：向数据表添加新列

Question

I'm using R shiny for creating a machine learning application. The app uses input widgets to to create the test obsevation, which then gets fed to a randomforest model and output an estimation when an actionbutton is clicked.

I want to store the input data that was selected, as well as the estimation and a timestamp in a datatable.

I am able to store all the selected input in a table, but I am having some trouble adding the 2 extra columns (estimation and timestamp) to the datatable.

Does anyone have an example of how to add new columns to a datatable? I am using the renderDataTable() and dataTableOutput() function to create the datatable.

This is the code for the server functions I found online for creating a datatable from input widgets:

server <- function(input, output, session) {

# Create the Log 
  saveData <- function(data) {
    data <- as.data.frame(t(data))
    if (exists("inputparameters")) {
      inputparameters <<- rbind(inputparameters, data)
    } else {
      inputparameters <<- data
    }
  }
  loadData <- function() {
    if (exists("inputparameters")) {
      inputparameters
    }
  }
  
  # Whenever a field is filled, aggregate all form data
  formData <- reactive({
    data <- sapply(fields, function(x) input[[x]])
    data
  })
  
  # When the Submit button is clicked, save the form data
  observeEvent(input$submit, {
    saveData(formData())
  })
  
  # Show the previous responses
  # (update with current response when Submit is clicked)
  output$inputparameters <- DT::renderDataTable({
    input$submit
    loadData()
  })
  
} # End Server function

How do I add new columns to the table in addition to the columns from input widgets?

Thanks in advance, I appreciate all your inputs.

Answer 1

Here's a solution that I've come up with:

library(shiny)
library(DT)

# datatable output function
dt_output = function(title, id) {
  fluidRow(column(
    12, h1(title)), # title
    hr(), DTOutput(id) # datatable output
  )
}
# render datatable function
render_dt = function(data, editable = 'cell', server = TRUE, ...) {
  renderDT(data, selection = 'none', server = server, editable = editable, ...)
}

# user interface
ui = fluidPage(
  
  # add button to add column
  actionButton(inputId = "addColumn", "New Column"),
  
  # custom column name
  textInput(inputId = "nameColumn", "New Column Name"),
  
  # title for page
  title = 'Double-click to edit table cells',
  # datatable output
  dt_output('Add Column Example")', 'x'),
  
  # add button to finish adding column and variables
  actionButton(inputId = "done", "Done"),
)


server <- function(input, output, session) {
  # use iris data as an reproducible example
  data = reactive({iris})
  
  # set up reactive value
  reactiveData = reactiveVal()
  
  # observe data
  observeEvent(data(),{
    reactiveData(data())
  })
  
  # showing only 5 rows per page
  options(DT.options = list(pageLength = 5))
  
  # make cells editable in our data
  output$x = render_dt(reactiveData(), 'cell')
  
  # edit a single cell
  proxy = dataTableProxy('x')
  observeEvent(input$x_cell_edit, {
    info = input$x_cell_edit
    newData <- reactiveData()
    newData[info$row, info$col] <- info$value
    reactiveData(newData)
    replaceData(proxy, reactiveData(), resetPaging = FALSE)
  })
  
  # add a column
  observeEvent(input$addColumn,{
    newData <- reactiveData()
    newData[[input$nameColumn]] <- numeric(length = nrow(newData))
    reactiveData(newData)
    replaceData(proxy, reactiveData(), resetPaging = FALSE)
    output$x = render_dt({
      reactiveData()
    })
  })
  
  # check for 'done' button press
  observeEvent(input$done, {
    stopApp(reactiveData())
  })
  
}

# run Shiny app
shinyApp(ui, server)

Because I don't have access to your data, I've provided a reproducible example using the iris dataset. I used this DT-edit example as the basis for the app.

As @Stéphane Laurent said, it's necessary to re-render the table (see # add a column ). The current data does not get lost but there is a glitch with the first value you enter (it resets the value). After, the first value it will no longer reset. I've also provide text input so that the new column can be named.

After pressing the "Done" button, the data will be output to your R console.

You can repeatedly press the "Add Column" button to produce columns.