Get and set substrings using their positions

Input vector. Either a character vector, or something coercible to one.

A pair of integer vectors defining the range of characters to extract (inclusive).

Alternatively, instead of a pair of vectors, you can pass a matrix to start. The matrix should have two columns, either labelled start and end, or start and length.

Single logical value. If TRUE, missing values in any of the arguments provided will result in an unchanged input.

replacement string