renderPrint: Text Output

Description Usage Arguments Details Value Examples

View source: R/shinywrappers.R

Description

renderPrint() prints the result of expr, while renderText() pastes it together into a single string. renderPrint() is equivalent to print(); renderText() is equivalent to cat(). Both functions capture all other printed output generated while evaluating expr.

renderPrint() is usually paired with verbatimTextOutput(); renderText() is usually paired with textOutput().

Usage

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

renderText(
  expr,
  env = parent.frame(),
  quoted = FALSE,
  outputArgs = list(),
  sep = " "
)

Arguments

expr

An expression to evaluate.

env

The environment in which to evaluate expr. For expert use only.

quoted

Is expr a quoted expression (with quote())? This is useful if you want to save an expression in a variable.

width

Width of printed output.

outputArgs

A list of arguments to be passed through to the implicit call to verbatimTextOutput() or textOutput() when the functions are used in an interactive RMarkdown document.

sep

A separator passed to cat to be appended after each element.

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.

Value

For renderPrint(), note the given expression returns NULL then NULL will actually be visible in the output. To display nothing, make your function return invisible().

Examples

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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'

})

Example output

[1] "foo"
[1] "1 2 3 4 5"

shiny documentation built on Jan. 26, 2021, 1:06 a.m.