[R] unique

[paladini]

Hello everybody,
I've got a problem concerning the function unique. I have got a 
data.frame "shopdata" with 1000 shop which were evaluated at different 
points in time.

With function subset I chose those shops with more then 10 employee and 
store it in data.frame "bigshopdata" with 700 shops.
  bigshopdata=subset(shopdata, shopdata$employee>10)

Now I use unique(bigshopdata$name) to ensure that each shop name is 
only listed  ones and not two or three times because of an evaluation at 
different dates.

What happens is that unique eliminates also those shops names which 
appear only ones in bigshopdata but twice or more often in shopdata.


But that is not what I want to. I'm only interessted in multiple 
appearance in bigshopdata not in an possible multible appearance in the 
original data.farme.


How can I use unique to get what I want? Or is there an alternative 
function?


I hope I explained the problem good enought.

Best regards


Claudia