In un messaggio del Thursday 03 June 2010, Clément Calenge ha scritto: > >So, I have three questions: is it only a date format issue or am I missing > >something else? If it is a date format issue, then, >how would it be > >possible to convert my dates in “YYyy-mm-dd” into “yymmdd”? and finally > >what loop functions or steps > could I take to create MCPs for the > >animals every two weeks. > > The error is not a date format issue, as the date is not required for the > calculation of the mcp. As the error message indicates, you need five > relocations or more to compute a minimum convex polygon. That is, if you > type: > > any(table(all.id)<5) > > If it returns TRUE, this means that for some animals, you have less than 5 > relocations, and so you cannot compute a MCP. To identify the animals that > are characterized by 5 relocations or more, try: > > ta <- table(all.id)<5 > ta[ta<5] > > And so, you can remove these animals, if you want to calculate a MCP for > each one: > > out <- names(ta[ta<5]) > pc <- mcp(all.xy[!(all.id%in%out),], factor(all.id[!(all.id%in%out)]) > plot(pc) > > Now concerning the loop every two weeks, it is hard to describe you what to > do without any data or precision on what you expect exactly... What are > the limits of the "pairs of weeks"? are they the same for all animals? are > you able to build a variable indicating the id of the "pairs of weeks" for > each relocation (e.g. "2007-09-04" is in the "pair" 1, etc.)? We need more > details... HTH,
Hi Abdi, list we made something similar to calculate "sesaonal" (see below) kernels for snowshoe hare. As Clément pointed out, the main issue is not "technical" (I mean, on the R side), but biological. Your "two weeks" timespan are probably not determined just on the base of a date but are in some way individual-dependant. Anyway, once you've determined the _exact_ date ranges that define each time interval (per animal or not) you can create a new column in your dataframe pasting together animal ID and a "fortnight ID". Using that new column as animal ID, any adehabitat homerange calculation can be done. Just to give the idea: for snowshoe hare we defined "sesaons" on an annual biological cycle basis (moult, breeding season, summer, winter moult, winter, etc), and then recoded (car::recode is rather handy here) a new variable called "period" (numbered from 1 to 5). The new ID was then assembled using animal ID and period, so that kernelUD was used to calculate separate home ranger per animal _and_ period. Again, problem is how those "two weeks" are defined. If you're interested in a detailed example I can dig out the script from our archive. HTH -- "Microwave oven? Whaddya mean, it's a microwave oven? I've been watching Channel 4 on the thing for two weeks." ----------------------------------------------------------- Damiano G. Preatoni, PhD Unità di Analisi e Gestione delle Risorse Ambientali Dipartimento Ambiente-Salute-Sicurezza Università degli Studi dell'Insubria Via J.H. Dunant, 3 - 21100 Varese (ITALY) tel +39 0332421538 fax +39 0332421446 http://biocenosi.dipbsf.uninsubria.it/ ICQ: 78690321 jabber: [email protected] skype: prea.net ----------------------------------------------------------- Please consider the environment before printing this email Please do not send attachments in proprietary formats http://www.gnu.org/philosophy/no-word-attachments.html Use the UNI CEI Standard ISO/IEC 26300:2006 ----------------------------------------------------------- O< stop html mail - http://www.asciiribbon.org
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