String edit distances

[kkranker]

Some users might want to add string edit "distances" or similarity "scores" to dtalink. The feature is not included because I wrote dtalink with the goal of using it with datasets that have millions of rows. I thought string edit distances would slow the package down too much. However, others request the feature from time to time.

I have no need to invest in implementing this feature myself. However, I am open to accepting a pull request if someone were to provide the feature (1) using well-written Mata code and (2) so long as it does not adversely affect runtimes for users who do not need the feature.

References:

• http://en.wikibooks.org/wiki/R_Programming/Text_Processing#Edit_distance
• http://en.wikipedia.org/wiki/Damerau%E2%80%93Levenshtein_distance
• https://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance
• http://alias-i.com/lingpipe/demos/tutorial/stringCompare/read-me.html
• https://ideas.repec.org/c/boc/bocode/s457547.html