R: Show the usage of a function

usage {formatR} | R Documentation

## Show the usage of a function

### Description

Print the reformatted usage of a function. The arguments of the function are searched by `argsAnywhere`, so the function can be either exported or non-exported in a package. S3 methods will be marked.

### Usage

    usage(FUN, width = getOption("width"), tidy = TRUE, output = TRUE,
        indent.by.FUN = FALSE, fail = c("warn", "stop", "none"))

### Arguments

`FUN` | the function name
`width` | the width of output
`tidy` | whether to reformat the usage code
`output` | whether to write the output to the console (via `cat`)
`indent.by.FUN` | whether to indent subsequent lines by the width of the function name (see “Details”)
`fail` | a character string that determines whether to generate a warning, stop, or do neither, if the width constraint is unfulfillable (default is `"warn"`)

### Details

Line breaks in the output occur between arguments. In particular, default values of arguments will not be split across lines.

When `indent.by.FUN` is `FALSE`, indentation is set by the option `getOption("formatR.indent", 4L)`, the default value of the `indent` argument of `tidy_source`.

### Value

The R code for the usage is returned as a character string (invisibly).

### See Also

`tidy_source`

### Examples

    library(formatR)
    usage(var)

    usage(plot)

    usage(plot.default)  # default method
    usage("plot.lm")  # on the 'lm' class

    usage(usage)

    usage(barplot.default, width = 60)  # output lines have 60 characters or less

    # indent by width of 'barplot('
    usage(barplot.default, width = 60, indent.by.FUN = TRUE)

    ## Not run:
    # a warning is raised because the width constraint is unfulfillable
    usage(barplot.default, width = 30)

    ## End(Not run)

[Package formatR version 1.5 Index]