Thank you for your help. The best I have found is to use the ddply function.
> pose
DESCRIPTION QUANITY CLOSING.PRICE
1 WHEAT May/10 1 467.75
2 WHEAT May/10 1 467.75
3 WHEAT May/10 1 467.75
4 WHEAT May/10 1 467.75
5 COTTON NO.2 May/10 1 78.13
6 COTTON NO.2 May/10 1 78.13
7 COTTON NO.2 May/10 1 78.13
> library(plyr)
> op=ddply(pose, c("DESCRIPTION","CLOSING.PRICE"),summarise, POSITION=
sum(QUANITY))
> op
DESCRIPTION CLOSING.PRICE POSITION
1 COTTON NO.2 May/10 78.13 3
2 WHEAT May/10 467.75 4
Op is a data.frame object.The trick is done!
***************************
Arnaud Gaboury
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BBM: 255B488F
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