Hi,
A few issues here. From your code it appears that the date you are feeding
as.ltraj is not unique (140403). You need to combine date and time then
convert to POSIXct. Another thing is that, as written, das is a character
vector (das <- as.character(data$NewDate)) which is what is being fed to
as.ltraj. You define das again as: das <-
as.POSIXct(strptime(as.character(data$NewDate). This should be throwing an
error since you did not give the format for strptime.
To rediscretize temporally or spatially see ?redisltraj.
--------------------------------------------------------
Jason G. Romine, Ph.D.
USGS Western Fisheries Research Center
5501A Cook-Underwood Road
Cook, WA 98605
Email:jromine at usgs.gov
Website: http://wfrc.usgs.gov
---------------------------------------------------------
On Sun, Feb 8, 2015 at 7:19 PM, alittle <alittle139 at gmail.com> wrote:
> I'm currently working on an first-passage time analysis under the
> adehabitatLT package. To begin, I'm trying to bring my data into R and run
> a
> simple set of movement metrics output by the ltraj function. My data
> consists of individual animal IDs, date, time, and x,y coordinates. I
> followed the adehabitatLT vignette but continue to get the following error:
>
> Error in as.ltraj(xy = data[, c("X", "Y")], date = das, id = data$NewID2,
> :
> non unique dates for a given burst
>
> My data is structured as follows:
>
> *NewID2 NewDate Time X Y*
> 1401FR141732 140403 6:57:00 PM 111111 2222222
> 1401FR141732 140403 7:37:00 PM 111123 2222243
> 1401FR141732 140403 7:57:00 PM 111135 2222264
> 1401FR141732 140403 8:17:00 PM 111147 2222285
> 1401FR141732 140403 8:37:00 PM 111159 2222306
> 1401FR141732 140403 8:57:00 PM 111171 2222327
> 1401FR141732 140403 9:17:00 PM 111183 2222348
> 1401FR141732 140403 9:37:00 PM 111195 2222369
> 1401FR141732 140403 9:57:00 PM 111207 2222390
> 1401FR141732 140403 10:17:00 PM 111219 2222411
> 1401FR141732 140403 10:37:00 PM 111231 2222432
> 1401FR141732 140403 11:17:00 PM 111243 2222453
>
> *R-code: *
>
> data<-read.csv("FPT_Ready_for_R_282015.csv")
> head(data)
>
> das <- as.character(data$NewDate)
> head(das)
> das <- as.POSIXct(strptime(as.character(data$NewDate)
>
> newcoon <- as.ltraj(xy = data[,c("X","Y")], date = das, id=data$NewID2,
> burst=data$NewID2,typeII = TRUE)
>
>
> The NewID2 was designed to be a unique ID for a unique first-passage time
> run and date. However, I continue to receive the same error about non
> unique
> dates for a given burst. This doesn't make sense given that I have a
> specific run for one animal on a specific date with individual times for
> each location. This coding doesn't seem to take into account the time
> between successive locations. Maybe I'm missing something.
>
> Additionally, the data is based on VHF locations; therefore, the time lag
> between successive locations is irregular. I eventually need to interpolate
> locations every 1-m along the path for the first-passage time analysis and
> I'm unclear on the exact process of how to do this using adehabitatLT.
>
> I appreciate any help on my issues. Thank you!
>
>
>
> --
> View this message in context:
> http://r-sig-ecology.471788.n2.nabble.com/Issue-with-ltraj-function-in-R-for-movement-analysis-tp7579295.html
> Sent from the r-sig-ecology mailing list archive at Nabble.com.
>
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