How can I use R to extract the time interval between visits of different species from camera trap images?
For example, Species A arrives at 07:00 (6 photos, each 1 min apart)
Species B arrives at 07:45 (so a 45 min time interval, or more precisely a 39 min time interval).
I have 10's of thousands of images, and I have used camtrapR to extract the record table, but the deltatime just tells me the time interval between photos of the same species same visit, not inter-species. I want to investigate the effect of species A's presence on species B.
Any advice?
Thanks Phillip! I actually hadn't had luck on this yet, and trying to write my own function went belly up... Thank you very much for the advice - I will try it out (hopefully soon) and report back on this thread for future answer-seekers
Hello Courtney Marneweck , did you have any luck with it? I am trying to do the same thing.
Ilona Papp unfortunately I haven't had chance yet to try out the above suggestion by Philip. I hope to in the next month or 2 - will post here when I do.
I came up with a different solution using loops, possibly not as elegant but working. It calculates time to event for each camera and for each event gives you first species and second species so you can analyse time difference for each combination (A to A, A to B, B to A and B to B).
I attached a simple plot do demonstrate it (for fox and dog records), but please keep in mind this is still work in progress. If you have any questions, I'll try answering them.
You need a dataframe with columns: date (POSIXct), camera ID (factor) and species (factor).
#create time to event subset dataframe for pair of species
tte
An important update (which I learned the hard way).
Do not simply calculate difference between the times like in the code I provided above. Problem is that R will change the unit of that time difference, it will be days when it is over 24h or hours when under 24, so 2.5 days and 2.5 hours will have the same value, obviously distorting the results.
Instead, use:
tte$timeDifference[i]
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