## Convert letters or numbers to their keypad counterpart

### Description

This function works best when converting numbers to letters, as each number only has a single possible letter. For each letter, there are 3 or 4 possible letters, resulting in a number of possible conversions. This function was intended to convert phonetic telephone numbers to their valid numeric equivalent; when used in this manner, each letter in a string can be lazily replaced without changing the rest of the string.

### Usage

keypad_convert(x, ext = FALSE)


### Arguments

 x A vector of characters or letters. ext logical; Should extension text be converted to numbers. Defaults to FALSE and matches x, ext, and extension followed by a space or number.

### Details

When replacing letters, this function relies on the feature of stringr::str_replace_all() to work with named vectors (c("A" = "2")).

### Value

If a character vector is supplied, a vector of each elements numeric counterpart is returned. If a numeric vector (or a completely coercible character vector) is supplied, then a list is returned, each element of which contacts a vector of letters for each number.

### Examples

keypad_convert("1-800-CASH-NOW ext123")