Efficacy of Degenerate Keyboard Maps
Efficacy of Degenerate Keyboard Maps
Some devices with limited size, such as smart phones, implement a reduced keyboard, with each key mapping to several letters. The effectiveness of the keyboard rests upon how well keystrokes distinguish between words of equal length. Keyboards with fewer than 26 keys map one key to a subset of letters. Then typing out a word often specifies a list of possibilities from which the intended word must be chosen.
The graphs here illustrate the balance between degeneracy and the number of keys for different mappings. For coarser mappings there are larger groups of words that share the same keystrokes. Each point represents the number of words with a certain degeneracy. The first point, for the group with degeneracy of one, on the left side, is for words that are totally differentiated by a particular keyboard map. The next point, degeneracy of two, is for words that have one other candidate word from the same keystrokes, and so on.