# roman

##### Roman Numerals

Simple manipulation of (a small set of) integer numbers as roman numerals.

- Keywords
- arith

##### Usage

```
as.roman(x)
.romans
```

##### Arguments

- x
a numeric or character vector of arabic or roman numerals.

##### Details

`as.roman`

creates objects of class `"roman"`

which are
internally represented as integers, and have suitable methods for
printing, formatting, subsetting, coercion, etc, see
`methods(class = "roman")`

.

Only numbers between 1 and 3899 have a unique representation as roman numbers.

`.romans`

is the basic dictionary, a named `character`

vector.

##### References

Wikipedia contributors (2006). Roman numerals. Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/w/index.php?title=Roman_numerals&oldid=78252134. Accessed September 29, 2006.

##### Examples

`library(utils)`

```
## First five roman 'numbers'.
(y <- as.roman(1 : 5))
## Middle one.
y[3]
## Current year as a roman number.
(y <- as.roman(format(Sys.Date(), "%Y")))
## Today, and 10, 20, 30, and 100 years ago ...
y - 10*c(0:3,10)
## mixture of arabic and roman numbers :
as.roman(c(NA, 1:3, "", strrep("I", 1:6))) # + NA with a warning for "IIIIII"
cc <- c(NA, 1:3, strrep("I", 0:5))
(rc <- as.roman(cc)) # two NAs: 0 is not "roman"
(ic <- as.integer(rc)) # works automitcally [without an explicit method]
## simple consistency checks -- arithmetic when result is in {1,2,..,3899} :
stopifnot(identical(rc, as.roman(rc)), # as.roman(.) is "idempotent"
identical(rc + rc + (3*rc), rc*5),
identical(ic, c(NA, 1:3, NA, 1:5)),
identical(as.integer(5*rc), 5L*ic),
identical(as.numeric(rc), as.numeric(ic)),
identical(as.list(rc), as.list(ic)))
```

*Documentation reproduced from package utils, version 3.4.1, License: Part of R 3.4.1*

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