Ltraj object without date.end
It looks to me that there must be a missing value in your date vector.
It's reproducible with a simple example modified from ?as.ltraj:
data(capreochiz)
## Create an object of class "ltraj"
cap <- as.ltraj(xy = capreochiz[,c("x","y")], date =
c(capreochiz$date[-nrow(capreochiz)], NA),
id = "Roe.Deer", typeII = TRUE,
infolocs = capreochiz[,4:8])
summary(cap)
id burst nb.reloc NAs date.begin date.end
1 Roe.Deer Roe.Deer 2355 0 2004-02-14 03:02:18 <NA>
So presumably you do have some missing values, perhaps the final lines
in the file are empty rows from Excel? (It's common).
Try any(is.na(Da)) to check.
Cheers, Mike.
On Tue, Feb 5, 2013 at 2:45 PM, John McEvoy <john.mcevoy at deakin.edu.au> wrote:
Hi Folks,
I?m having some trouble with creating ltraj objects from irregular GPS data. I run the same code on two different csv files with identical columns, number formats etc but get two different results. The only difference between these files are the values of lat/lon and the date-time stamp. I cannot find any extreme values that might be throwing things out. My main problem is that I keep getting ltraj objects with no defined ?date.end?. Why would this be happening? I hope it?s something simple. Code below. Thanks for your time,
John
##using "as.ltraj" to create a trajectory from GPS data in adehabitatLT
data<-read.csv("Animal_1.csv", na.strings="NA")
head(data)
# ID Date Latitude Longitude
#1 Animal_1 2010-12-12 12:30:00 -30.55900 136.8788
#2 Animal_1 2010-12-12 14:30:00 -30.55867 136.8788
#3 Animal_1 2010-12-12 16:30:00 -30.55883 136.8788
#4 Animal_1 2010-12-12 18:30:00 -30.55883 136.8788
#5 Animal_1 2010-12-12 20:30:00 -30.55833 136.8790
#6 Animal_1 2010-12-12 22:30:00 -30.55883 136.8788
Da<-strptime(data$Date,format='%Y-%m-%d %H:%M:%S')
Da<-as.POSIXct(Da)
xy<-data[,c("Longitude", "Latitude")]
id<-data$ID
TRAJAnimal_1<-as.ltraj(xy,id,date=Da, burst=id)
summary(TRAJAnimal_1)
# id burst nb.reloc NAs date.begin date.end
#1Animal_1 Animal_1 2169 0 2010-12-12 12:30:00 2011-08-28 08:30:00
##############################################################################
##running the same code for another file with the same columns, same formats and i get a trajectory with no "date.end"
data<-read.csv("Animal_2.csv", na.strings="NA")
head(data)
# ID Date Latitude Longitude
#1 Animal_2 2010-05-15 20:30:00 -33.82517 138.6078
#2 Animal_2 2010-05-15 22:30:00 -33.82400 138.6085
#3 Animal_2 2010-05-16 00:30:00 -33.82400 138.6085
#4 Animal_2 2010-05-16 02:30:00 -33.82400 138.6085
#5 Animal_2 2010-05-16 04:30:00 -33.82400 138.6085
#6 Animal_2 2010-05-16 08:30:00 -33.82233 138.6060
Da<-strptime(data$Date,format='%Y-%m-%d %H:%M:%S')
Da<-as.POSIXct(Da)
xy<-data[,c("Longitude", "Latitude")]
id<-data$ID
TRAJAnimal_2<-as.ltraj(xy,id,date=Da, burst=id)
summary(TRAJAnimal_2)
# id burst nb.reloc NAs date.begin date.end
#Animal_2 Animal_2 2858 0 2010-05-15 20:30:00 <NA>
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Michael Sumner Hobart, Australia e-mail: mdsumner at gmail.com