ECOTOXr (version 1.2.1)

cas: Functions for handling chemical abstract service (CAS) registry numbers

Description

Functions for handling chemical abstract service (CAS) registry numbers

Usage

cas(length = 0L)
is.cas(x)
as.cas(x)
# S3 method for cas
[[(x, i)
# S3 method for cas
[(x, i)
# S3 method for cas
[[(x, i) <- value
# S3 method for cas
[(x, i) <- value
# S3 method for cas
format(x, hyphenate = TRUE, ...)
# S3 method for cas
as.character(x, ...)
show.cas(x, ...)
# S3 method for cas
print(x, ...)
# S3 method for cas
as.list(x, ...)
# S3 method for cas
as.double(x, ...)
# S3 method for cas
as.integer(x, ...)
# S3 method for cas
c(...)
# S3 method for cas
as.data.frame(...)

Value

Functions cas, c and as.cas return S3 class 'cas' objects. Coercion functions (starting with 'as') return the object as specified by their respective function names (i.e., integer, double, character, list and data.frame). The show.cas and print functions also return formatted charaters. The function is.cas will return a single logical value, indicating whether x is a valid S3 cas-class object. The square brackets return the selected index/indices, or the vector of cas objects where the selected elements are replaced by value.

Arguments

length

A non-negative integer specifying the desired length. Double values will be coerced to integer: supplying an argument of length other than one is an error.

x

Object from which data needs to be extracted or replaced, or needs to be coerced into a specific format. For nearly all of the functions documented here, this needs to be an object of the S3 class 'cas', which can be created with as.cas. For as.cas, x can be a character (CAS registry number with or without hyphenation) or a numeric value. Note that as.cas will only accept correctly formatted and valid CAS registry numbers.

i

Index specifying element(s) to extract or replace. See also base::Extract().

value

A replacement value, can be anything that can be converted into an S3 cas-class object with as.cas.

hyphenate

A logical value indicating whether the formatted CAS number needs to be hyphenated. Default is TRUE.

...

Arguments passed to other functions

Author

Pepijn de Vries

Details

In the database CAS registry numbers are stored as text (type character). As CAS numbers can consist of a maximum of 10 digits (plus two hyphens) this means that each CAS number can consume up to 12 bytes of memory or disk space. By storing the data numerically, only 5 bytes are required. These functions provide the means to handle CAS registry numbers and coerce from and to different formats and types.

Examples

## This will generate a vector of cas objects containing 10
## fictive (0-00-0), but valid registry numbers:
cas(10)

## This is a cas-object:
is.cas(cas(0L))

## This is not a cas-object:
is.cas(0L)

## Three different ways of creating a cas object from
## Benzene's CAS registry number (the result is the same)
as.cas("71-43-2")
as.cas("71432")
as.cas(71432L)

## This is one way of creating a vector with multiple CAS registry numbers:
cas_data <- as.cas(c("64175", "71432", "58082"))

## This is how you select a specific element(s) from the vector:
cas_data[2:3]
cas_data[[2]]

## You can also replace specific elements in the vector:
cas_data[1] <- "7440-23-5"
cas_data[[2]] <- "129-00-0"

## You can format CAS numbers with or without hyphens:
format(cas_data, TRUE)
format(cas_data, FALSE)

## The same can be achieved using as.character
as.character(cas_data, TRUE)
as.character(cas_data, FALSE)

## There are also show and print methods available:
show(cas_data)
print(cas_data)

## Numeric values can be obtained from CAS using as.numeric, as.double or as.integer
as.numeric(cas_data)

## Be careful, however. Some CAS numbers cannot be represented by R's 32 bit integers
## and will produce NA's. This will work OK:
huge_cas <- as.cas("9999999-99-5")

if (FALSE) {
## This will not:
as.integer(huge_cas)
}

## The trick applied by this package is that the final
## validation digit is stored separately as attribute:
unclass(huge_cas)

## This is how cas objects can be concatenated:
cas_data <- c(huge_cas, cas_data)

## This will create a data.frame
as.data.frame(cas_data)

## This will create a list:
as.list(cas_data)