Wow, can't imagine that was actually the problem!
Thank you so much Mathieu for your help and quick replies!
 
Date: Thu, 21 Nov 2013 07:41:32 -0800
From: ml-node+s471788n7578532h45@n2.nabble.com
To: nickvandoormaal26@hotmail.com
Subject: Re: Adehabitat Ltraj error message: "non unique dates for a given burst"



	Ah! I didn't spot that in the first place, but you gave a wrong format to 

the strptime function! The one you gave implied a '12-03-20 00:04' format. 

As a result, all of them returned NAs (well, almost all of them... Might be 

worth looking at the ten that went through it).


You need to use %Y instead of %y.


Mathieu.



Le 11/21/2013 05:58 AM, NickvanDoormaal a écrit :

> Thank you so much for your quick reply Mathieu!

>

> I tried your suggestion:

> sum(duplicated(paste(da, march2012df$ID)))

> [1] 2587

>

> I was surprised by this large number, so I checked how many rows many dataset has:

> nrow(march2012)

> [1] 2597

>

> This almost exactly the same, only a difference of 10 (maybe because of the 10 individuals?).

> It seems that all the dates are identified as duplicates...

>

>

>

> Date: Wed, 20 Nov 2013 06:11:26 -0800

> From: [hidden email]

> To: [hidden email]

> Subject: Re: Adehabitat Ltraj error message: "non unique dates for a given burst"

>

>

>

> 	Hi Nick,

>

>

> You can try:

>

>

> sum(duplicated(paste(da, march2012df$ID)))

>

>

> and from there, if the sum is > 0, identify the duplicates *per individual*.

>

>

> As far as I can tell, the function as.ltraj works at the burst level, in

>

> your cases individuals.

>

>

> Mathieu.

>

>

>

> Le 11/20/2013 07:21 AM, Nick van Doormaal a écrit :

>

>> Hello everyone,

>

>>

>

>> I'm trying to create a ltraj-class.

>

>> I start with importing an excel file containing all the relocations (in this case for the month March) into ArcMap and create a shapefile. Next I load the shapefile into R and transform the coordinates to UTM37S.

>

>>

>

>> My dataset looks as follows:

>

>>

>

>> head(march2012)

>

>>    coordinates                           ID                                       Date_old        Longitude   Latitude           Date

>

>> 0 (496297, 9688770)  Emusaya_Male  2012-03-20   38.96668   -2.815783  2012-03-20 00:04

>

>> 1 (496670, 9686680)  Emusaya_Male  2012-03-20   38.97003   -2.834650  2012-03-20 01:04

>

>> 2 (497136, 9685230)  Emusaya_Male  2012-03-20   38.97423   -2.847833  2012-03-20 02:04

>

>> 3 (497233, 9684700)  Emusaya_Male  2012-03-20   38.97510   -2.852633  2012-03-20 03:05

>

>> 4 (497105, 9684290)  Emusaya_Male  2012-03-20   38.97395   -2.856317  2012-03-20 04:04

>

>> 5 (497281, 9683830)  Emusaya_Male  2012-03-20   38.97553   -2.860467  2012-03-20 05:04

>

>>

>

>> I used the following script:

>

>> da <- as.character(march2012$Date)

>

>> da <- as.POSIXct(strptime(as.character(march2012$Date),"%y-%m-%d  %H:%M"))

>

>> march2012df <- as.data.frame(march2012)

>

>> xymarch2012 <- coordinates(march2012)

>

>> elemarch2012 <- as.ltraj(xy =xymarch2012, date = da, id = march2012df$ID)

>

>>

>

>> There error message I got was: "Error in as.ltraj(xy = xymarch2012, date = da, id = march2012df$ID) :

>

>>     non unique dates for a given burst".

>

>>

>

>> Before posting this message, I read about duplicates. My dataset includes 10 different elephants, so it could be that some dates are the same. However, I would like to keep these locations because they are different individuals.

>

>>

>

>> I hope I made my problem clear. If you need any more information, please let me know what kind of information and how to send it.

>

>>

>

>> Kind regards,

>

>>

>

>> Nick van Doormaal

>

>> MSc student Forest and Nature Conservation

>

>> Wageningen University, The Netherlands 		 	   		

>

>> 	[[alternative HTML version deleted]]

>

>>

>

>> _______________________________________________

>

>> R-sig-ecology mailing list

>

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>

>> https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
>>

>

>

>

> _______________________________________________

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-- 


~$ whoami

Mathieu Basille, PhD


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(+1) 954-577-6314

http://ase-research.org/basille

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Et je manque de temps, et je manque d'audace. »

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