I know this question is very simple, but I am not figure it out


 

I have the data frame:


 

 


 

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))


 

test


 

  year    x   y   z


 

1 2000 54 29 26


 

2 2000 41  2  68


 

3 2001 90 92 46


 

4 2001 15 22 51


 

 


 

I want to sum the vectors x, y and z within each year (2000 and 2001) to obtain this:


 

 


 

year       x   y    z


 

1 2000  95  31 94


 

2 2001 105 114 97


 

 


 

I tried tapply but did not work (or probably I do it wrong)


 

 


 

Any suggestions?  


 

 


 

silva
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