Nice extension. Note that is has a bug: you have hard-coded the database table prefix "wiki_" instead of using the global variable $wgDBprefix. So instead of
SELECT rev_user_text FROM wiki_page...
You should have:
SELECT rev_user_text FROM {$wgDBprefix}page...
Etc.
Anybody know if there's a SQL-to-gnuplot widget to directly plot the data returned by SQL queries?
DanB