Dear group, I have this following data.frame:
> c DESCRIPTION CREATED.DATE QUANITY CLOSING.PRICE 26 PRM HGH GD ALU 2010-04-09 -1 2,415.9000 27 PRM HGH GD ALU 2010-04-09 1 2,415.9000 28 PRIMARY NICKEL 2010-03-04 1 25,755.7100 29 PRIMARY NICKEL 2010-03-05 -1 25,755.7100 30 PRIMARY NICKEL 2010-03-10 -1 25,760.8600 31 PRIMARY NICKEL 2010-03-10 1 25,760.8600 32 STANDARD LEAD 2010-04-01 1 2,355.9600 33 STANDARD LEAD 2010-04-01 -1 2,355.9600 34 STANDARD LEAD 2010-04-01 1 2,355.9600 35 STANDARD LEAD 2010-04-01 -1 2,355.9600 36 STANDARD LEAD 2010-04-01 -1 2,355.9600 37 STANDARD LEAD 2010-04-01 1 2,355.9600 38 STANDARD LEAD 2010-04-01 -1 2,355.9600 39 STANDARD LEAD 2010-04-06 1 2,357.1200 40 STANDARD LEAD 2010-04-08 1 2,420.7300 41 SPCL HIGH GRAD 2010-04-08 1 2,420.7300 42 SPCL HIGH GRAD 2010-04-08 -1 2,420.7300 43 SPCL HIGH GRAD 2010-04-09 -1 2,421.0500 44 SPCL HIGH GRAD 2010-04-09 1 2,421.0500 45 SPCL HIGH GRAD 2010-04-09 -1 2,421.0500 46 SPCL HIGH GRAD 2010-04-09 1 2,421.0500 47 SPCL HIGH GRAD 2010-04-09 1 2,421.0500 48 SPCL HIGH GRAD 2010-01-13 1 2,388.4300 49 SPCL HIGH GRAD 2010-01-25 -1 2,388.4300 The goal is to get a smaller df, with only PRM HGH GD ALU, PRIMARY NICKEL, STANDARD LEAD, STANDARD LEAD as rows, with QUANITY column as a sum of QUANITY, DATE column as the max CREATED.DATE with the corresponding CLOSING.PRICE. If I pass this : > op=ddply(c, c("DESCRIPTION"), summarise, POSITION= sum(QUANITY),DATE=max(CREATED.DATE)) It returns this : > op DESCRIPTION POSITION DATE 1 PRIMARY NICKEL 0 2010-03-10 2 PRM HGH GD ALU 0 2010-04-09 3 SPCL HIGH GRAD 2 2010-04-09 4 STANDARD LEAD 0 2010-04-06 Not bad, as I have my 4 elements, the sum of QUANITY for each one, the max DATE for each one, BUT I would like to add the CLOSING.PRICE column with the CLOSING.PRICE corresponding to the max date. I have no idea how to do this. Any help would be appreciated. TY ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.