Here's another approach using the plyr package:
# Function to process each row of input:
g <- function(d) {
y <- unlist(d$observations)
if(length(y) > 0)
data.frame(site = d$site, sector = d$sector, y = y) else NULL
}
library('plyr')
> ddply(input, .(site), g)
site sector y
1 1 north 1
2 1 north 2
3 1 north 3
4 2 south 4
5 2 south 3
6 4 west 14
7 4 west 12
8 4 west 53
9 4 west 2
10 4 west 4
11 5 east 3
12 6 south 23
HTH,
Dennis
On Sat, Oct 22, 2011 at 4:51 PM, Peter Meilstrup
<peter.meilst...@gmail.com> wrote:
> The setup: I have a data frame where one column is in list mode, and
> each entry contains a vector of varying length.
> I want to expand this into a data frame with one row for each member
> of the list-mode column (the other values being replicated)
>
> For example, an example input and the desired output would be:
>
> input <- data.frame(site = 1:6,
> sector = factor(c("north", "south", "east",
> "west", "east", "south")),
> observations =
> I(list(c(1,2,3),c(4,3),c(),c(14,12,53,2,4),c(3),c(23))))
>
> desired.output <-
> data.frame(site = c(1,1,1,2,2,4,4,4,4,5,6),
> sector = factor(c(2,2,2,3,3,4,4,4,4,4,1,3),
> labels = c("east", "north", "south", "west")),
> observations = c(1,2,3,4,3,14,12,53,2,4,3,23))
>
> There seems like there ought to be a good (simple, fast) way to do
> this, but I've been struggling. Any ideas?
>
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