R: Type Conversion on Character Variables

type.convert {utils}

R Documentation

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

`x`	a character vector.
`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.

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.

Value