[ESS] How to use ess-fix-EQ-assign

[Douglas Bates]

Sorry to keep asking versions of the same questions - the memory and
the knees are the first things to go as you get older.  :-)

I was sent an R source file where the author uses = for assignment.  I
would like to replace the assignment ='s only by <- and I know there
are clever ways in ESS of doing this but I can't seem to get them
working.  Can someone point me in the correct direction?