R: Printable Output

renderPrint {shiny} | R Documentation

## Printable Output

### Description

Makes a reactive version of the given function that captures any printed output, and also captures its printable result (unless `invisible`), into a string. The resulting function is suitable for assigning to an `output` slot.

### Usage

    renderPrint(expr, env = parent.frame(), quoted = FALSE,
      width = getOption("width"), outputArgs = list())

### Arguments

`expr` | An expression that may print output and/or return a printable R object.
`env` | The environment in which to evaluate `expr`.
`quoted` | Is `expr` a quoted expression (with `quote()`)? This is useful if you want to save an expression in a variable.
`width` | The value for `options('width')`.
`outputArgs` | A list of arguments to be passed through to the implicit call to `verbatimTextOutput` when `renderPrint` is used in an interactive R Markdown document.

### Details

The corresponding HTML output tag can be anything (though `pre` is recommended if you need a monospace font and whitespace preserved) and should have the CSS class name `shiny-text-output`.

The result of executing `func` will be printed inside a `capture.output` call.

Note that unlike most other Shiny output functions, if the given function returns `NULL` then `NULL` will actually be visible in the output. To display nothing, make your function return `invisible()`.

### See Also

`renderText` for displaying the value returned from a function, instead of the printed output.

### Examples

    isolate({

    # renderPrint captures any print output, converts it to a string, and
    # returns it
    visFun <- renderPrint({ "foo" })
    visFun()
    # '[1] "foo"'

    invisFun <- renderPrint({ invisible("foo") })
    invisFun()
    # ''

    multiprintFun <- renderPrint({
      print("foo");
      "bar"
    })
    multiprintFun()
    # '[1] "foo"\n[1] "bar"'

    nullFun <- renderPrint({ NULL })
    nullFun()
    # 'NULL'

    invisNullFun <- renderPrint({ invisible(NULL) })
    invisNullFun()
    # ''

    vecFun <- renderPrint({ 1:5 })
    vecFun()
    # '[1] 1 2 3 4 5'

    # Contrast with renderText, which takes the value returned from the function
    # and uses cat() to convert it to a string
    visFun <- renderText({ "foo" })
    visFun()
    # 'foo'

    invisFun <- renderText({ invisible("foo") })
    invisFun()
    # 'foo'

    multiprintFun <- renderText({
      print("foo");
      "bar"
    })
    multiprintFun()
    # 'bar'

    nullFun <- renderText({ NULL })
    nullFun()
    # ''

    invisNullFun <- renderText({ invisible(NULL) })
    invisNullFun()
    # ''

    vecFun <- renderText({ 1:5 })
    vecFun()
    # '1 2 3 4 5'

    })

[Package shiny version 1.0.5 Index]