Phone Number

Introduction to phonenumber

This document describes the usage of the two functions in the phonenumber package. Note that, though this package’s functions convert back and forth from numbers to English letters as on a telephone’s keypad. Note that the length of the character string need not conform to any standard length telephone number.

phonenumber’s functions

letterToNumber
numberToLetter

Telephone keypad

For purposes of this package, the mapping of numbers to letters on a telephone’s keypad are as follows:

2 corresponds to A, B, C
3 corresponds to D, E, F
4 corresponds to G, H, I
5 corresponds to J, K, L
6 corresponds to M, N, O
7 corresponds to P, Q, R, S
8 corresponds to T, U, V
9 corresponds to W, X, Y, Z
1 and 0 do not have corresponding letters

(I am aware that on some telephones, primarily older models, Q and Z are mapped to 0 rather than to 7 and 9.)

`letterToNumber`

letterToNumber converts a string containing letters into the corresponding numbers on a telephone’s keypad. For example, if the user wants to know what telephone number corresponds to “Texas:”

string <- "Texas"
letterToNumber(string)

## [1] "83927"

The function is not limited to letters, though. Any numeric characters are returned as is and any non-alphanumeric characters (including spaces) are converted to dashes (-) and 1 and 0 are returned as is:

string <- "Texas is #1"
letterToNumber(string)

## [1] "83927-47--1"

`numberToLetter`

numberToLetter converts a string containing numbers into the corresponding letters on a telephone’s keypad. For example, if the user wants to know what possible character strings could be spelled by a sequence of numbers (e.g., 22):

string <- "22"
numberToLetter(string)

## [1] "AA" "AB" "AC" "BA" "BB" "BC" "CA" "CB" "CC"

The function is not limited to numbers, though. Any alphabetic characters are returned as is and any non-alphanumeric characters (including spaces) are converted to dashes (-) and 1 and 0 are returned as is:

string <- "806!"
numberToLetter(string)

## [1] "T0M-" "T0N-" "T0O-" "U0M-" "U0N-" "U0O-" "V0M-" "V0N-" "V0O-"