type.convert {utils}

R Documentation

Convert Data to Appropriate Type

Description

Convert a data object to logical, integer, numeric, complex, character or factor as appropriate.

Usage

type.convert(x, ...)
## Default S3 method:
type.convert(x, na.strings = "NA", as.is, dec = ".",
             numerals = c("allow.loss", "warn.loss", "no.loss"),
             tryLogical = TRUE, ...)
## S3 method for class 'data.frame'
type.convert(x, ...)
## S3 method for class 'list'
type.convert(x, ...)

Arguments

x	a vector, matrix, array, data frame, or list.
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	whether to store strings as plain character. When false, convert character vectors to factors. 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. 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 character, depending on as.is.
tryLogical	a logical determining if vectors consisting entirely of F, T, FALSE, TRUE and na.strings should be converted to logical; true, by default.
...	arguments to be passed to or from methods.

Details

This helper function is used by read.table. When the data object x is a data frame or list, the function is called recursively for each column or list element.

Given a vector, the function attempts to convert it to logical, integer, numeric or complex, and when additionally as.is = FALSE (no longer the default!), converts a character vector to factor. 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.

If tryLogical is true as by default, vectors containing just F, T, FALSE, TRUE and values from na.strings are converted to logical. This may be surprising in a context where you have many character columns with e.g., 1-letter strings and you happen to get one with only "F". In such cases tryLogical = FALSE is recommended. 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 or (for as.is = FALSE) factors.

Since this is a helper function, the caller should always pass an appropriate value of as.is.

Value

An object like x but using another storage mode when appropriate.

Author(s)

R Core, with a contribution by Arni Magnusson

See Also

read.table, class, storage.mode.

Examples

## Numeric to integer
class(rivers)
x <- type.convert(rivers, as.is = TRUE)
class(x)

## Convert many columns
auto <- type.convert(mtcars, as.is = TRUE)
str(mtcars)
str(auto)

## Convert matrix
phones <- type.convert(WorldPhones, as.is = TRUE)
storage.mode(WorldPhones)
storage.mode(phones)

## Factor or character
chr <- c("A", "B", "B", "A")
ch2 <- c("F", "F", "NA", "F")
(fac <- factor(chr))
type.convert(chr, as.is = FALSE) # -> factor
type.convert(fac, as.is = FALSE) # -> factor
type.convert(chr, as.is = TRUE)  # -> character
type.convert(fac, as.is = TRUE)  # -> character
type.convert(ch2, as.is = TRUE)                   #-> logical
type.convert(ch2, as.is = TRUE, tryLogical=FALSE) #-> character

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