Several answers to your question are already available here:
http://lists.faunalia.it/pipermail/animov/2010-June/000601.html
http://lists.faunalia.it/pipermail/animov/2010-June/000602.html
Please avoid cross-posting,
Best,

Clément Calenge


On 06/03/2010 04:18 PM, Abdi, Abdulhakim wrote:
> Dear List,
>
> I'm trying to detect patterns in the movements of a nomadic gazelle species during the breeding season. Basically, I would like to create MCPs (minimum convex polygons representing home ranges) for each of the 32 gazelles every two weeks starting on September 4th 2007. I have satellite tracking points from September 2007 to January 2010. The point of this exercise is to see whether the animals converge at particular areas during the breeding season or whether the site selection is random.
>
> Before going into the date loop procedure I attempted to create MCPs for the animals without regard for the two-week interval:
>
> Here is what my data.frame looks like:
>
>    
>> head(all.frame)
>>      
>     Name    Status       X       Y       Date
> 1 76792   capture 1356206 2196167 2007-09-04
> 2 76795   capture 1354434 2209845 2007-09-04
> 3 76797   capture 1354434 2209845 2007-09-04
>
> And here is the output of the command, as you can see I get an error statement:
>
>    
>> all.xy = all.frame[,c("X","Y")]
>> all.id = all.frame$Name
>> all.mcp = mcp(all.xy, all.id, percent=95)
>>      
> Error in mcp(all.xy, all.id, percent = 95) :
>    At least 5 relocations are required to fit an home range
>
> Next, I ran MCPs for the "puechabon$loc" data.frame that comes with Adehabitat and it worked without producing any errors, so I compared my data.frame with puechabon$loc.
>
>    
>> head(puechabon$loc)
>>      
>     Name Age Sex      X       Y   Date
> 1 Brock   2   1 699889 3161559 930701
> 2 Brock   2   1 700046 3161541 930703
> 3 Brock   2   1 698840 3161033 930706
>
> Looking at the structure of both, my dataset has the date set to class 'Date' while in the Puechabon dataset it's set to 'Integer' and the dates are concatenated as "yymmdd":
>
>    
>> str(all.frame)
>>      
> 'data.frame':   5059 obs. of  5 variables:
>   $ Name  : Factor w/ 32 levels "76790","76792",..: 2 5 7 7 1 3 5 8 7 7 ...
>   $ Status: Factor w/ 3 levels "argos","capture",..: 2 2 2 3 2 2 1 2 3 3 ...
>   $ X     : int  1356206 1354434 1354434 1349773 1362802 1362802 1357468 1362802 1345648 1345387 ...
>   $ Y     : int  2196167 2209845 2209845 2211725 2216920 2216920 2176051 2216920 2213362 2213572 ...
>   $ Date  :Class 'Date'  num [1:5059] 13760 13760 13760 13761 13761 ...
>
>    
>> str(puechabon$loc)
>>      
> 'data.frame':   119 obs. of  6 variables:
>   $ Name: Factor w/ 4 levels "Brock","Calou",..: 1 1 1 1 1 1 1 1 1 1 ...
>   $ Age : int  2 2 2 2 2 2 2 2 2 2 ...
>   $ Sex : int  1 1 1 1 1 1 1 1 1 1 ...
>   $ X   : int  699889 700046 698840 699809 698627 698719 698991 698626 698879 699756 ...
>   $ Y   : int  3161559 3161541 3161033 3161496 3160941 3160989 3161015 3160768 3160964 3161449 ...
>   $ Date: int  930701 930703 930706 930707 930708 930709 930713 930714 930715 930720 ...
>
> I tried to convert my dates to the "yymmdd" format, without any luck as the new column came out exactly the same as the original one:
>
>    
>> all.frame$Date2 = as.Date(all.frame$Date, format="%y/%m%/d")
>> head(all.frame)
>>      
>     Name    Status       X       Y       Date      Date2
> 1 76792   capture 1356206 2196167 2007-09-04 2007-09-04
> 2 76795   capture 1354434 2209845 2007-09-04 2007-09-04
> 3 76797   capture 1354434 2209845 2007-09-04 2007-09-04
>
> So, I have three questions: is it only a date format issue or am I missing something else? If it is a date format issue, then, how would it be possible to convert my dates in "YYyy-mm-dd" into "yymmdd"? and finally what loop functions or steps could I take to create MCPs for the animals every two weeks.
>
> Any help is greatly appreciated.
>
> Regards,
>
> Hakim Abdi
>
> _________________________________
> Abdulhakim Abdi, M.Sc.
> Research Intern
>
> Conservation GIS/Remote Sensing Lab
> Smithsonian Conservation Biology Institute
> 1500 Remount Road
> Front Royal, VA
> phone: +1-540-635-6578
> fax: +1-540-635-6506
> email: abdia@si.edu<mailto:abdia@si.edu>
>
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>
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>
>    


-- 
Clément CALENGE
Cellule d'appui à l'analyse de données
Office national de la chasse et de la faune sauvage
Saint Benoist - 78610 Auffargis
tel. (33) 01.30.46.54.14


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