[R-sig-eco] as.ltraj in adehabitat

[Struve, Juliane]

Hello,
many thanks for replying ! In the example there are 4 observations for 18/06/2006, at 4 different times, 2 observations for 05/09/2006 at two different times andso on. My data are in excel files, one per individual.
I use this code to read in and prepare the example data set:

library(PBSmapping)
library(adehabitat)
track_1646=read.table("AllChange_1646R.txt", sep="\t", header=TRUE)
attr(track_1646, "projection") <- c("LL")
track_1646.utm <- convUL(track_1646)
track_1646 <- track_1646.utm
#colnames(track_1646) <- c("X","Y","date","id","burst","Time","ID","VR2number")
id <- as.character(track_1646$id)
burst <- as.character(track_1646$burst)
date <- as.POSIXct(strptime(as.character(track_1646$date),"%d/%m/%Y"))
as.ltraj(track_1646, date, id, burst,typeII = TRUE, slsp = c("remove", "missing"))

The last line yields the error message. I am not really sure about the burst argument, and I do not know why as.traj () needs it. Can you shed light on this ?
Many thanks for your time. 
Juliane 


________________________________________
From: Stéphane Dray [dray at biomserv.univ-lyon1.fr]
Sent: 27 March 2009 15:01
To: Struve, Juliane
Cc: r-sig-ecology at r-project.org
Subject: Re: [R-sig-eco] as.ltraj in adehabitat

Juliane,
it seems that you have two relocations observed at the same time.
Without details (e.g., what did you type in R), it is difficult to give
you a more precised answer.

Cheers.

Struve, Juliane wrote:
> Dear list,
>
> I am trying to convert a dataframe into an ltraj object and have a hard time defing the burst argument. The data consist of locations, dates and  time for only one individual (id=1646). An example is given below. The individual may have been seen several times during one day at several different locations. When I try to convert the dataframe I get error message
>
> Error in as.ltraj(track_1646, date, id, burst, typeII = TRUE, slsp = c("remove",  :
>   non unique dates for a given burst
> Would somebody be able to help ?
>
> Thank you very much for your time.
>
> Juliane
>
>
> X       Y                       date                   id      burst          Time       ID      VR2number
> -82.5632        27.303  18/08/2006      1646    1646    08:48:59        64      32
> -82.5605        27.30237 18/08/2006      1646    1646    09:53:20        63      30
> -82.5632        27.303  18/08/2006      1646    1646    13:27:48        121     32
> -82.5737        27.31475 18/08/2006      1646    1646    20:39:18        91      33
> -82.5445        27.27731 05/09/2006      1646    1646    22:17:52        3243    19
> -82.5356        27.2716 05/09/2006      1646    1646    23:29:38        16319   20
> -82.5445        27.27731 08/09/2006      1646    1646    23:34:30        3904    19
> -82.5356        27.2716 09/09/2006      1646    1646    02:39:48        25023   20
>
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Stéphane DRAY (dray at biomserv.univ-lyon1.fr )
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