[R-sig-eco] Strange calculation of dt in adehabitat

[Anders Kagervall]

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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