st: Dropping observations with similar names (same prefix)

["Ben Ammar" <Ben-Ammar@gmx.de>]

Hi everybody,

Sorry for bothering you but I was wondering how to drop observations (string)that merely differ in the last letter?
For example:

City           Population     #household
London A          400             34
London B          300             12
London F          600             66 
Hamburg B         200             54
Hamburg G         400             59 
  ...             ...
  ...             ...
How can I drop those rows in which the Prefix (London, Hamburg)is the same,
so that I only keep the first mentioned one(London A, Hamburg B)?
Currently I do have 30,000 obs making a hand collection pretty difficult.
First I tried
.drop if name==substr(name,-2,-10) & name[_n-1]==substr(name,-2,-10)

However 0 observations are deleted so I think the "&" sign is the problem (and in addition the length of the string differs from obs to obs...probably that's causing some problem, too)therfore, I tried:
.drop if name==substr(name,-2,-10) == name[_n-1]==substr(name,-2,-10)

but that resulted in a 'type mismatch'.
Also I tried an approach like in the FAQs by creating an index for
each suffix (" A"=1," B"=2,"C" etc.). However, I'm not sure if this does does necessarily exclude all possibilities how those observations could occur. 

Thanks for your help!
Ben Ammar
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