[R] Odp: Collapsing panel data
Petr PIKAL
petr.pikal at precheza.cz
Tue Feb 3 10:10:06 CET 2009
Hi
r-help-bounces at r-project.org napsal dne 03.02.2009 09:43:04:
>
>
> Dear R-helpers,
>
> I've been thinking about this for some time, maybe someone can help. I
have
> a fairly large dataset with thousands of firms, call the a, b, c, etc..
> such as
>
> [,1] [,2]
> [1,] "A" 0.5
> [2,] "" 0.2
> [3,] "" 0.3
> [4,] "B" 0.1
> [5,] "" 0.9
> [6,] "C" 0.4
>
> Or to put it differently two vectors such as
>
> y <- c("A", "", "", "B", "", "C")
> x <- c(0.5, 0.2, 0.3, 0.1, 0.9, 0.4)
>
> The empty lines "" always belong to the firm above. Now I want to
collapse
> the dataset so that each firm (A,B, C, etc) has one line only, using
> summation.
>
> So what I would like is
>
> yNew <- c("A", "B", "C")
> xNew <- c(1, 1, 0.4)
That is what are NA values for. There are quite useful functions for
handling them.
y <- c("A", "", "", "B", "", "C")
x <- c(0.5, 0.2, 0.3, 0.1, 0.9, 0.4)
y[y==""]<-NA
from package zoo
y.na<-na.locf(y)
tapply(x,y.na, sum)
A B C
1.0 1.0 0.4
or aggregate(...)
Regards
Petr
>
> The problem I'm having is that each firm has a different number of
entries
> for x, so some like C have just one and others have ten or more, so I
have
> difficulty imagining how to use a loop in this case.
> I'd be greatful for any suggestions.
> Karina
>
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