[R-sig-eco] Strange calculation of dt in adehabitat
Anders Kagervall
Anders.Kagervall at vfm.slu.se
Mon Jul 12 16:36:54 CEST 2010
Hi Matt,
>From: Matt Beard [mailto:biozealot21 at gmail.com]
>Sent: den 10 juli 2010 04:35
>To: Anders Kagervall
>Cc: r-sig-ecology at r-project.org
>Subject: Re: [R-sig-eco] Strange calculation of dt in adehabitat
>
>Anders,
>I was not able to recreate your problem with the demo you provided. What are the details of your platform?
Here is my sessionInfo()
R version 2.10.1 (2009-12-14)
i386-pc-mingw32
locale:
[1] LC_COLLATE=Swedish_Sweden.1252 LC_CTYPE=Swedish_Sweden.1252
[3] LC_MONETARY=Swedish_Sweden.1252 LC_NUMERIC=C
[5] LC_TIME=Swedish_Sweden.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] gpclib_1.5-1 adehabitat_1.8.3 ade4_1.4-14
>
I also ran the test with Linux and R 2.11.1 and got the same results.
However, your comment made me think a little further and I'm now pretty sure that the problem comes from the fact that 2008-10-26 was a date when we changed from daylight savings time to normal time. I tested by replacing the month from 10 to 09 in the data file and got results without any missing points.
I'm still not sure if the problem I see is in how we record time in our database or how adehabitat calculates the time interval. I will re-run the analyze using GMT-datetime, that we also have in the database, and see if I can get rid of the problem.
ps
Your assumption about the precision of the X and Y coordinates was correct. I have now attached the actual data file I used.
ds
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