Dear Contributors
I would like to perform this operation using a loop, instead of repeating
the same operation many times.
The numbers from 1 to 4 related to different groups that are in the
database and for which I have the same data.


    x<-c(1,3,7)

datiP1 <- datiP[datiP$city ==1,x];

datiP2 <- datiP[datiP$city ==2,x];

datiP3 <- datiP[datiP$city ==3,x]

datiP4 <- datiP[datiP$city ==4,x];
-- 

Thank you for any help you can provide.

Francesca

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