type.convert: Type Conversion on Character Variables
Description
Convert a character vector to logical, integer, numeric, complex or
factor as appropriate.Usage
type.convert(x, na.strings = "NA", as.is = FALSE, dec = ".",
numerals = c("allow.loss", "warn.loss", "no.loss"))Arguments
na.strings
a vector of strings which are to be interpreted as
NA values. Blank fields are also considered to be
missing values in logical, integer, numeric or complex vectors. as.is
logical. See ‘Details’.
dec
the character to be assumed for decimal points.
numerals
string indicating how to convert numbers whose
conversion to double precision would lose accuracy, typically when
x has more digits than can be stored in a double.
Can be abbreviated. Possible values are
numerals = "allow.loss", default:- the conversion
happens with some accuracy loss. This has been the only
behavior of R versions 3.0.3 and earlier.
numerals = "warn.loss":- a
warning
about accuracy loss is signalled and the conversion happens as
with numerals = "allow.loss".
numerals = "no.loss":x is not
converted to a number, but to a factor or left as
character, depending on as.is. This has been the only
behavior of R version 3.1.0.
Value
An atomic vector or (for as.is = FALSE) a factor.Details
This is principally a helper function for read.table.
Given a character vector, it attempts to convert it to logical,
integer, numeric or complex, and failing that converts it to factor
unless as.is = TRUE. The first type that can accept all the
non-missing values is chosen. Vectors which are entirely missing values are converted to logical,
since NA is primarily logical. Vectors containing just F, T, FALSE, TRUE
and values from na.strings are converted to logical. Vectors
containing optional whitespace followed by decimal constants
representable as R integers or values from na.strings are
converted to integer. Other vectors containing optional whitespace
followed by other decimal or hexadecimal constants (see
NumericConstants), or NaN, Inf or infinity
(ignoring case) or values from na.strings are converted to
numeric. Where converting inputs to numeric or complex would result
in loss of accuracy they can optionally be returned as strings (for
as.is = TRUE) or factors. Since this is a helper function, the caller should always pass an
appropriate value of as.is.