
Dear list,
I have the following problem. I have a data frame like this



CLUSTER        YEAR      variable        Delta         R_pivot
M1                     2005         EC01           NA              NA                    

M1                     2006         EC01            2                NA

M1                     2007         EC01            4                5

M2                     2005          EC01          NA              NA

M2                     2006          EC01           5                NA

M2                     2007          EC01           8                 7

M1                     2005          EC02           NA               NA

M1                     2006          EC02            3                 NA

M1                    2007            EC02           1                 8

M2                    2005            EC02           NA               NA

M2                    2006            EC02           9                 NA

M2                    2007            EC02            6                 10




I'm trying to build the time series of the variables by applying the following formulas in a recursive way(by starting from the value of R_pivot at time 2007)

R_EC01(2006)=R_EC01(2007)-Delta_EC01(2007)

R_EC01(2005)=R_EC01(2006)-Delta_EC01(2006)
In terms of number I would have:
R_EC01(2006)=5-4=1
R_eco1(2005)=1-2=-1

And the same should be done for variable EC02. In addition, this calculations should be down grouping by variable e cluster..so the result should be
CLUSTER        YEAR      variable        series

M1                     2005         EC01             -1                


M1                     2006         EC01             1


M1                     2007         EC01              5


M2                     2005          EC01             -6



M2                     2006          EC01             -1

M2                     2007          EC01              7



M1                     2005          EC02              4

M1                     2006          EC02               7


M1                    2007            EC02              8


M2                    2005            EC02             -5


M2                    2006            EC02            4


M2                    2007            EC02             10
I applied the following formula which gives me a partial good result but not at all:
series=ddply(x,.(variable,CLUSTER),transform,series=rev(c(R_pivot,rev(R_pivot-cumsum(rev(Delta[-1]))))))
Thanks for your attention!!!









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