R: Reporting progress (functional API)

withProgress {shiny} | R Documentation

## Reporting progress (functional API)

### Description

Reports progress to the user during long-running operations.

### Usage

    withProgress(expr, min = 0, max = 1, value = min + (max - min) * 0.1,
      message = NULL, detail = NULL, style = getShinyOption("progress.style",
      default = "notification"), session = getDefaultReactiveDomain(),
      env = parent.frame(), quoted = FALSE)

    setProgress(value = NULL, message = NULL, detail = NULL,
      session = getDefaultReactiveDomain())

    incProgress(amount = 0.1, message = NULL, detail = NULL,
      session = getDefaultReactiveDomain())

### Arguments

`expr` | The work to be done. This expression should contain calls to `setProgress`.
`min` | The value that represents the starting point of the progress bar. Must be less tham `max`. Default is 0.
`max` | The value that represents the end of the progress bar. Must be greater than `min`. Default is 1.
`value` | Single-element numeric vector; the value at which to set the progress bar, relative to `min` and `max`.
`message` | A single-element character vector; the message to be displayed to the user, or `NULL` to hide the current message (if any).
`detail` | A single-element character vector; the detail message to be displayed to the user, or `NULL` to hide the current detail message (if any). The detail message will be shown with a de-emphasized appearance relative to `message`.
`style` | Progress display style. If `"notification"` (the default), the progress indicator will show using Shiny's notification API. If `"old"`, use the same HTML and CSS used in Shiny 0.13.2 and below (this is for backward-compatibility).
`session` | The Shiny session object, as provided by `shinyServer` to the server function. The default is to automatically find the session by using the current reactive domain.
`env` | The environment in which `expr` should be evaluated.
`quoted` | Whether `expr` is a quoted expression (this is not common).
`amount` | For `incProgress`, the amount to increment the status bar. Default is 0.1.

### Details

This package exposes two distinct programming APIs for working with progress. Using `withProgress` with `incProgress` or `setProgress` provide a simple function-based interface, while the `Progress` reference class provides an object-oriented API.

Use `withProgress` to wrap the scope of your work; doing so will cause a new progress panel to be created, and it will be displayed the first time `incProgress` or `setProgress` are called. When `withProgress` exits, the corresponding progress panel will be removed.

The `incProgress` function increments the status bar by a specified amount, whereas the `setProgress` function sets it to a specific value, and can also set the text displayed.

Generally, `withProgress`/`incProgress`/`setProgress` should be sufficient; the exception is if the work to be done is asynchronous (this is not common) or otherwise cannot be encapsulated by a single scope. In that case, you can use the `Progress` reference class.

As of version 0.14, the progress indicators use Shiny's new notification API. If you want to use the old styling (for example, you may have used customized CSS), you can use `style="old"` each time you call `withProgress()`. If you don't want to set the style each time `withProgress` is called, you can instead call `shinyOptions(progress.style="old")` just once, inside the server function.

### See Also

`Progress`

### Examples

    ## Only run examples in interactive R sessions
    if (interactive()) {
    options(device.ask.default = FALSE)

    ui <- fluidPage(
      plotOutput("plot")
    )

    server <- function(input, output) {
      output$plot <- renderPlot({
        withProgress(message = 'Calculation in progress',
                     detail = 'This may take a while...', value = 0, {
          for (i in 1:15) {
            incProgress(1/15)
            Sys.sleep(0.25)
          }
        })
        plot(cars)
      })
    }

    shinyApp(ui, server)
    }

[Package shiny version 1.0.3 Index]