Convert Roman Numerals to Integers

Convert roman numerals to integers

roman2int(roman)

Arguments

roman

character vector containing roman numerals

Value

A integer vector with the same length as roman. Character strings which are not valid roman numerals will be converted to NA.

Details

This function will convert roman numerals to integers without the upper bound imposed by R (3899), ignoring case.

See also

as.roman

Author

Gregory R. Warnes greg@warnes.net

Examples

roman2int(c("I", "V", "X", "C", "L", "D", "M"))
#>    I    V    X    C    L    D    M 
#>    1    5   10  100   50  500 1000 

# works regardless of case
roman2int("MMXVI")
#> MMXVI 
#>  2016 
roman2int("mmxvi")
#> MMXVI 
#>  2016 

# works beyond R's limit of 3899
val.3899 <- "MMMDCCCXCIX"
val.3900 <- "MMMCM"
val.4000 <- "MMMM"
as.numeric(as.roman(val.3899))
#> [1] 3899
as.numeric(as.roman(val.3900))
#> [1] 3900
as.numeric(as.roman(val.4000))
#> [1] 4000

roman2int(val.3899)
#> MMMDCCCXCIX 
#>        3899 
roman2int(val.3900)
#> MMMCM 
#>  3900 
roman2int(val.4000)
#> MMMM 
#> 4000