[R] basic question

[Christoph Lehmann]

sapply(split(test, test$year), function(x) list(x.s = sum(x$x), y.s = 
sum(x$y), z.s = sum(x$z)))


or for one variable only

aggregate(test$x, list(id = test$year), sum)

cheers
christoph

jose silva wrote:
> I know this question is very simple, but I am not figure it out
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> I have the data frame:
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> test<- data.frame(year=c(2000,2000,2001,2001),x=c(54,41,90,15), y=c(29,2,92,22), z=c(26,68,46,51))
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> test
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>   year    x   y   z
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> 1 2000 54 29 26
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> 2 2000 41  2  68
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> 3 2001 90 92 46
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> 4 2001 15 22 51
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> I want to sum the vectors x, y and z within each year (2000 and 2001) to obtain this:
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> year       x   y    z
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> 1 2000  95  31 94
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> 2 2001 105 114 97
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> I tried tapply but did not work (or probably I do it wrong)
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> Any suggestions?  
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> silva
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