[R] Calculating home ranges using mcp in adehabitat

[Tom Mason]

Hello,

I've been trying to calculate home range sizes (for Icelandic geese!) using
minimum convex polygons with the adehabitat package. I've tried to use the R
code shown by demo(homerange) in adehabitat and when that didn't work I've
fiddled around with it but to no avail...Below is the output of the demo
that I've attempted to follow, followed by a subset of my data (for one
individual) and the code I've been trying. Can anyone tell me where I may be
going wrong???


#Demo output...

> data(puechabon)

> xy<-puechabon$locs[,c("X","Y")]

> id<-puechabon$locs$Name

> ## The data are:
> xy[1:4,]     ## relocations coordinates
       X       Y
1 699889 3161559
2 700046 3161541
3 698840 3161033
4 699809 3161496

> id[1:4]      ## ID
[1] Brock Brock Brock Brock
Levels: Brock Calou Chou Jean

> ###############################################
> ###############################################
> ###
> ### Home ranges
> 
> ## MCP
> hr<-mcp(xy, id)         ## home range estimation



# My attempts...

> mydata
   Name         X        Y
1  XDRY -21.98389 64.06457
2  XDRY -21.99759 64.08291
3  XDRY -21.98784 64.06467
4  XDRY -21.98333 64.06058
5  XDRY -21.97889 64.06257
6  XDRY -21.98284 64.06044
7  XDRY -21.97886 64.06358
8  XDRY -21.99741 64.08124
9  XDRY -21.99715 64.08330
10 XDRY -22.00397 64.09331
11 XDRY -21.99811 64.08239
12 XDRY -22.00453 64.09337
13 XDRY -21.99713 64.08299
14 XDRY -21.99608 64.08307
15 XDRY -21.99646 64.08352
16 XDRY -21.99326 64.08361
17 XDRY -22.00770 64.09090
18 XDRY -21.98160 64.06400
19 XDRY -21.97966 64.06367

> xy<-mydata$locs[,c("X","Y")]
> id<-mydata$locs$Name

> xy[1:19,]
NULL
> id[1:19,]
NULL

> mcp(xy,id,percent=95)
Error in if (length(id) != nrow(xy)) stop("xy and id should be of the same
length") : 
  argument is of length zero


#I've also tried things like the code below. But didn't know how to
incorporate 'locs' into this...

> xy<-cbind(X,Y)
> id<-Name[1:19]

> xy[1:19,]
              X        Y
 [1,] -21.98389 64.06457
 [2,] -21.99759 64.08291
 [3,] -21.98784 64.06467
 [4,] -21.98333 64.06058
 [5,] -21.97889 64.06257
 [6,] -21.98284 64.06044
 [7,] -21.97886 64.06358
 [8,] -21.99741 64.08124
 [9,] -21.99715 64.08330
[10,] -22.00397 64.09331
[11,] -21.99811 64.08239
[12,] -22.00453 64.09337
[13,] -21.99713 64.08299
[14,] -21.99608 64.08307
[15,] -21.99646 64.08352
[16,] -21.99326 64.08361
[17,] -22.00770 64.09090
[18,] -21.98160 64.06400
[19,] -21.97966 64.06367

> id<-Name[1:19]
> id[1:19]
 [1] XDRY XDRY XDRY XDRY XDRY XDRY XDRY XDRY XDRY XDRY XDRY
[12] XDRY XDRY XDRY XDRY XDRY XDRY XDRY XDRY
Levels: XDRY

> mcp(xy,id,percent=95)
Error in apply(xy, 2, mean) : dim(X) must have a positive length

> xy1<-xy[1:19,]
> id1<-id[1:19]
> mcp(xy1,id1,percent=95)
Error in apply(xy, 2, mean) : dim(X) must have a positive length


Would be most grateful for any suggestions to where I'm going wrong!


Tom Mason,
University of Exeter,
UK.








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