On Apr 15, 2010, at 3:50 AM, arnaud Gaboury wrote:
> Dear group,
>
> Here is a data.frame, "lme":
>
>> lme
> DESCRIPTION CLOSING.PRICE POSITION
> 4 PRIMARY NICKEL USD 04/06/10 25,755.7100 0
> 5 PRIMARY NICKEL USD 10/06/10 25,760.8600 0
> 6 PRM HGH GD ALUMINIUM USD 09/07/10 2,415.9000 0
> 8 SPCL HIGH GRADE ZINC USD 06/07/10 2,420.1000 -1
> 9 SPCL HIGH GRADE ZINC USD 07/07/10 2,420.4100 -1
> 10 SPCL HIGH GRADE ZINC USD 08/07/10 2,420.7300 1
> 11 SPCL HIGH GRADE ZINC USD 09/07/10 2,421.0500 1
> 12 SPCL HIGH GRADE ZINC USD 13/04/10 2,388.4300 0
> 13 SPCL HIGH GRADE ZINC USD 14/04/10 2,389.0000 0
> 14 SPCL HIGH GRADE ZINC USD 15/04/10 2,389.5700 0
> 15 SPCL HIGH GRADE ZINC USD 17/05/10 2,402.2900 0
> 16 SPCL HIGH GRADE ZINC USD 18/05/10 2,402.6400 -2
>
> DESCRIPTION and CLOSING.PRICE are factors, POSITION is numeric.
Lacking a reproducible example ... that is one that can be readily
pasted into a console session ... this code remains untested and
probably full of bugs so it is more a pseudo-code approach to the
problem than a solution:
DESCRIPgrep <- sub(".{13}$", "", lme$DESCRIPTION,
perl=TRUE)
with( lme, tapply(as.numeric(as.character(CLOSING.PRICE),
DESCRIPgrep, mean)
Please reread the Posting Guide and submit data examples constructed
with dput or dump so that responders can work on representative data.
It would be a real pain to reconstruct that data example but you could
have trivially offered it for testing.
>
> I want to sum POSITION by products, i.e. PRIMARY NICKEL, PRM HGH GD
> ALUMINIUM and SPCL HIGH GRADE ZINC. The problem is that, as you can
> see,
> there is a different date as a part of each product description. Can
> anyone
> tell me how to get rid of these dates so I can sum the position
> column? The
> number of rows is not fixed and will change every day.
>
> TY.
--
David Winsemius, MD
West Hartford, CT