[AniMov] RES: Adehabitat: creating MCPs every two weeks for 32 different animals

Milton Cezar Ribeiro miltinho_astronauta at yahoo.com.br
Thu Jun 3 16:35:15 CEST 2010


Hi Abdi,

 

How many points you get per id with table(all.id)?

 

Cheers

milton

 

 

De: animov-bounces at faunalia.it [mailto:animov-bounces at faunalia.it] Em nome
de Abdi, Abdulhakim
Enviada em: Thursday, June 03, 2010 11:19 AM
Para: AniMov at faunalia.it
Assunto: [AniMov] Adehabitat: creating MCPs every two weeks for 32 different
animals

 

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 at si.edu

 

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