renderPrint

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.

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.

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().

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'

})
[1] "foo"

[1] "1 2 3 4 5"

See also

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