filesstrings (version 0.4.0)

ExtractNumbers: Extract numbers (or non-numbers) from a string.

Description

ExtractNumbers extracts the numbers (or non-numbers) from a string where decimals are optionally allowed. ExtractNonNumerics extracts the bits of the string that aren't extracted by ExtractNumbers. NthNumber is a convenient wrapper for ExtractNumbers, allowing you to choose which number you want. Similarly NthNonNumeric. Please view the examples at the bottom of this page to ensure that you understand how these functions work, and their limitations. These functions are vectorised over string.

Usage

ExtractNumbers(string, leave.as.string = FALSE, decimals = FALSE,
  leading.decimals = FALSE, negs = FALSE)
ExtractNonNumerics(string, decimals = FALSE, leading.decimals = FALSE,
  negs = FALSE)
NthNumber(string, n, leave.as.string = FALSE, decimals = FALSE,
  leading.decimals = FALSE, negs = FALSE)
NthNonNumeric(string, n, decimals = FALSE, leading.decimals = FALSE,
  negs = FALSE)

Arguments

string

A string.

leave.as.string

Do you want to return the number as a string (TRUE) or as numeric (FALSE, the default)?

decimals

Do you want to include the possibility of decimal numbers (TRUE) or not (FALSE, the default).

leading.decimals

Do you want to allow a leading decimal point to be the start of a number?

negs

Do you want to allow negative numbers? Note that double negatives are not handled here (see the examples).

n

The index of the number (or non-numeric) that you seek. Negative indexing is allowed i.e. n = 1 will give you the first number (or non-numeric) whereas n = -1 will give you the last number (or non-numeric), n = -2 will give you the second last number and so on.

Value

For ExtractNumbers and ExtractNonNumerics, a list of numeric or character vectors, one list element for each element of string. For NthNumber and NthNonNumeric, a vector the same length as string (as in length(string), not nchar(string)).

Details

If any part of a string contains an ambiguous number (e.g. 1.2.3 would be ambiguous if decimals = TRUE (but not otherwise)), the value returned for that string will be NA. Note that these functions do not know about scientific notation (e.g. 1e6 for 1000000).

Examples

ExtractNumbers(c("abc123abc456", "abc1.23abc456"))
ExtractNumbers(c("abc1.23abc456", "abc1..23abc456"), decimals = TRUE)
ExtractNumbers("abc1..23abc456", decimals = TRUE)
ExtractNumbers("abc1..23abc456", decimals = TRUE, leading.decimals = TRUE)
ExtractNumbers("abc1..23abc456", decimals = TRUE, leading.decimals = TRUE,
leave.as.string = TRUE)
ExtractNumbers("-123abc456")
ExtractNumbers("-123abc456", negs = TRUE)
ExtractNumbers("--123abc456", negs = TRUE)
ExtractNonNumerics("abc123abc456")
ExtractNonNumerics("abc1.23abc456")
ExtractNonNumerics("abc1.23abc456", decimals = TRUE)
ExtractNonNumerics("abc1..23abc456", decimals = TRUE)
ExtractNonNumerics("abc1..23abc456", decimals = TRUE,
leading.decimals = TRUE)
ExtractNonNumerics(c("-123abc456", "ab1c"))
ExtractNonNumerics("-123abc456", negs = TRUE)
ExtractNonNumerics("--123abc456", negs = TRUE)
ExtractNumbers(c(rep("abc1.2.3", 2), "a1b2.2.3", "e5r6"), decimals = TRUE)
ExtractNumbers("ab.1.2", decimals = TRUE, leading.decimals = TRUE)
NthNumber("abc1.23abc456", 2)
NthNumber("abc1.23abc456", 2, decimals = TRUE)
NthNumber("-123abc456", -2, negs = TRUE)
ExtractNonNumerics("--123abc456", negs = TRUE)
NthNonNumeric("--123abc456", 1)
NthNonNumeric("--123abc456", -2)