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: [email protected]<mailto:[email protected]>
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