[tlocoh-info] Hull metrics

elikana kalumanga ekalumanga at yahoo.com
Mon Feb 16 03:04:23 CET 2015

 Hi people,
I am at the very initial stages of learning tlocoh so that I can estimate home ranges and calculate revisitation rate of elephants. While creating an xyt.lxy object, I constantly receive error message; Error in min(xy[, 1]) : invalid 'type' (S4) of argument. I will be happy to know what is going wrong with my code? 
Thanks, and here are my codes:  

> head(FRAcoordinates)
         x       y
0 386924.1 9369662
1 387761.6 9369931

> head(as.character(FRA$Date_))
[1] "2012-08-31 20:09:00.000" "2012-08-31 16:09:00.000" "2012-08-31 12:09:00.000"
[4] "2012-08-31 8:10:00.000"  "2012-08-31 4:09:00.000"  "2012-08-31 0:11:00.000" 
> FRA.localtime[1:3]
[1] "2012-08-31 23:09:00 EAT" "2012-08-31 19:09:00 EAT" "2012-08-31 15:09:00 EAT"

> FRA.lxy <- xyt.lxy(xy=FRA, dt=FRA.localtime, id="FRA",proj4string=CRS("+proj=utm +south +zone=36 +ellps=WGS84"))
Error in min(xy[, 1]) : invalid 'type' (S4) of argument

/ElikanaUniversity of Dar es Salaam-Tanzania 

     On Wednesday, February 11, 2015 7:33 PM, Andy Lyons <lyons.andy at gmail.com> wrote:

   Hi Julia, 
 That's a good question. It seems you need a way to identify hulls that belong to specific sites, and save the site location as an ancillary variable (which can then serve as a hull metric). There isn't a function currently in the package that can classify points or hulls based on their location in space, but we could develop one because I think this would have general utility. 
 How specifically would you want to assign points / hulls to sites? One option for defining a site would be with a polygon, either by drawing one on the plot window or bringing in a shapefile. Another option would be defining a site based on distance from a given location (i.e., a circle). After defining the site, would you want to say that any point (and thus the hull for that point) that falls within the site? Or would you only want hulls whose entire area falls within the site? 
 Comment from other people welcome also. 
 On Feb 11, 2015, at 5:53 AM, Julia Krejci <julia.krejci at chello.at> wrote: 
   Dear Mailinglist, I’m currently trying to compare hull metrics (nsv and mnlv) of several individuals and several sites. I want to know how long and how often individual A visited site 1 and 2 and the same for individual B. Is there a way to get more accurate values for specific sites than I can receive from the images? Currently I have just plotted the hpp with the respective colour code and try to compare colours but of course that’s not very accurate, also because the colours only represent ranges of values (like, yellow is 1 – 12, orange is 12 – 24 and so  on).  Thank you for every advice! Best wishes,  Julia   _______________________________________________
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