Sebastien -
Since you didn't provide a reproducible example, I may
be off track, but here's how I'd handle the problem.
Suppose the data set with nest_id, LD, and FD is called mydata.
First create a function to find the percentage of active nests for
a given time:
pctact = function(time)100*sum(mydata$LD <= time & mydata$FD >= time)/nrow(dat)
Now create the vector of dates you're interested in
dts = 60:273
Finally use sapply to evaluate the percentage at each date:
answer = data.frame(dts,sapply(dts,pctact))
If this isn't what you're looking for, a reproducible example
would be helpful.
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spec...@stat.berkeley.edu
On Wed, 15 Dec 2010, Sébastien Rioux wrote:
Hi All,
I've been struggling on that one for a couple of days. I've tried several
things, but nothing is worth publishing.
I'm working with a bird nests data frame for which I have a laying date (LD)
and a fledgling date (FD) (in calendar Julian date) by nest id. For the
period spanning between LD and SD, the nest is termed "active". Each nest id
occur once in the data frame.
How could I get the cumulative percentage of active nests by date within a
specified time frame ? Let's say from Julian date 60 to 273 ?
I would like the results to look like this :
Julian_date prct_ active
60 0
61 5
62 10
63 25
...
Here is an example of the data frame
nest_id LD FD
1 193 219
2 131 159
3 196 221
4 152 179
5 136 164
?
Cheers,
Sebastien
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