<div dir="ltr"><div>Hi Anna:<br><br></div>Here is my response<br><div><div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, May 12, 2014 at 6:56 AM, Anna Schweiger <span dir="ltr"><<a href="mailto:anna.schweiger@nationalpark.ch" target="_blank">anna.schweiger@nationalpark.ch</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div link="blue" vlink="purple" lang="DE-CH"><div><p class="MsoNormal"><span lang="EN-US">Dear T-LoCoH group, dear Andy<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US">First of all: I want to thank Andy and his colleagues for the great effort you are putting into T-LoCoH! I have started to use the package some weeks ago and I have to say, that I’ve hardly ever came across such a well explained tutorial (everything worked right from the start!)! Your publication is also really helpful and easy to follow and so are the R help files. Thank you so much! Good documentations make life a lot easier (and work fun)!!! <u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US">However, I have a couple of questions I could not figure out myself. Maybe someone has some ideas on the following:<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p><p style="margin-left:18pt"><u></u><span lang="EN-US"><span>1.<span style="font:7pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US">The first is a methodological question: I’m comparing the feeding areas of ibex and chamois in the summers of four consecutive years in one valley where they co-occur. For each year I have several (1-7) individuals per species. My assumptions are that individuals of the same species behave more similar then individuals of different species. In a first step, I chose the same values for s and a (I use the “a” method) for all individuals of the same species, across the years; i.e. all ibex have the same s and a value and all chamois another s and a value. However, I could also argue that the individuals of one species behave more similar in the same year than in the other years (maybe because of environmental variability). Therefore, I was wondering if selecting different s and a values for every year makes sense? In the end I’m extracting environmental data based on the polygons defined by what can be called “core feeding areas” (I select them based on duration of stay and number of separate visits). Then I compare the two species in GLMMs. So I’m basically pooling all ibex data (different ind, different years) and compare them to all chamois. I can account for the individual and yearly differences by including animal ID and year as a random effect. Still, I believe the parameters of all individuals from one species should be somewhat comparable. So far I could not quite get my head around this problem: Should I choose only one s and a value per species, or maybe only one for both species, or is it possible to vary s and a per year or even per individual? Do you have any suggestions? For me this is really tricky.</span></p>
</div></div></blockquote><div><br></div><div>You need to use the same s and a values for all species. However, you can ask the question, how robust is my result to variations in a and s. Thus you could see if your result holds up for all a and s or breaks down as these change. If it does break down, then this break down might have some significant implications because the implication might be that differences emerge or disappear, as the case may be, when time is given more or less weighting <br>
</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div link="blue" vlink="purple" lang="DE-CH"><div><p style="margin-left:18pt"><span lang="EN-US"><u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">My other questions are more technical: <u></u><u></u></span></p><p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p><p style="margin-left:18pt"><u></u><span lang="EN-US"><span>2.<span style="font:7pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US">I want to manually offset duplicate xy points in xyt.lxy. Is this possible? I want to avoid random offset when constructing hulls, to make the analysis repeatable. Maybe the explanation is somewhere in the help, but I couldn’t find it…</span></p>
</div></div></blockquote><div><br></div><div>Since time is unique, I don't see how you can have overlapping points unless they are true duplicates. Such duplicates must be removed. So I am not sure I understand your question.<br>
<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div link="blue" vlink="purple" lang="DE-CH"><div><p style="margin-left:18pt"><span lang="EN-US"><u></u><u></u></span></p>
<p style="margin-left:18pt"><u></u><span lang="EN-US"><span>3.<span style="font:7pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US">I’m resampling my data by using lxy.thin.byfreq (common sampling interval should be 4h, some individuals have 2h, some 10 min frequencies). Now, I have some cases with time gaps of about 1 month. I would still like to include these data. Is it possible to split the data and include the two time periods separately? Can this be done by setting a value for tct in the auto.a method? I don’t quite understand how tct works. </span></p>
</div></div></blockquote><div><br></div><div>Andy will have to explain how this works. <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div link="blue" vlink="purple" lang="DE-CH">
<div><p style="margin-left:18pt"><span lang="EN-US"><u></u><u></u></span></p><p style="margin-left:18pt"><u></u><span lang="EN-US"><span>4.<span style="font:7pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US">Again about resampling: As recommended in the help I thin bursts before resampling the data to a common time interval. I was wondering if the following is correct: First I inspect the sampling frequency plot with lxy.plot.freq. Then I thought: When tau.diff.max (default) = 0.02 and tau (median)=120 min, sampling frequencies between 117.6 - 122.4 should be fine. If I now see points in the plot with let’s say delta t/tau = 0.95, then sampling frequency= 0.95*120= 108 min which is outside the range of tau.diff.max. In that case, should I set the threshold value in lxy.thin.bursts to thresh=0.98, to make sure all remaining points fall within the range 117.6 - 122.4? I think that having a sampling interval of 108 min in a dataset that should have 120 min is not uncommon and normally I would not think it is problematic. But I have only a very vague idea about the effects of such data intervals when the algorithms start working. Is it possible to provide any guidelines on thresholds for thinning bursts? </span></p>
</div></div></blockquote><div><br>Again, Andy will have to explain how this works. <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div link="blue" vlink="purple" lang="DE-CH">
<div><p style="margin-left:18pt"><span lang="EN-US"><u></u><u></u></span></p><p style="margin-left:18pt"><u></u><span lang="EN-US"><span>5.<span style="font:7pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US">And related to the question above: Should I check and thin burst again after resampling to a new time interval (with the new range of tau values?)?</span></p>
</div></div></blockquote><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div link="blue" vlink="purple" lang="DE-CH"><div><p style="margin-left:18pt">
<span lang="EN-US"><u></u><u></u></span></p><p style="margin-left:18pt"><u></u><span lang="EN-US"><span>6.<span style="font:7pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US">Generally, it is a bit hard for me to choose parameters based on visual interpretation (s, a, delta/tau etc. ). So far I came to the conclusion that this is the best I can do. However, I was wondering if there are any general arguments to support the choices one makes based on visual interpretation. Do you have an opinion on this? How could you argue (I’m thinking about future referees…)?</span></p>
</div></div></blockquote><div><br></div><div>There are arguments that one can use to justify one choice over another. These are based on entropy concepts, but we have yet to discuss or implement these methods. So I cannot be more specific at this time. <br>
</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div link="blue" vlink="purple" lang="DE-CH"><div><p style="margin-left:18pt"><span lang="EN-US"><u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">I think that’s it for the moment. I would really appreciate any help or comments! </span></p></div></div></blockquote><div><br></div><div>Good luck and all the best<br><br>wayne<br>
<br> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div link="blue" vlink="purple" lang="DE-CH"><div><p class="MsoNormal"><span lang="EN-US"><u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US">All the best, <u></u><u></u></span></p><p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p><p class="MsoNormal">
<span lang="EN-US">Anna <u></u><u></u></span></p><p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US">P.S.: I’m not sure if this helps, but I think I came across some typos in the R help file. Just in case somebody is collecting them: <u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">xyt.lxy: To disable the checking for duplicate time stamps, pass dup.dt.check=<span style="background:none repeat scroll 0% 0% lime">TRUE.</span> <u></u><u></u></span></p><p class="MsoNormal">
<span lang="EN-US">lxy.thin.bursts {tlocoh}: To identify whether there are bursts in a LoCoH-xy dataset, and the sampling frequency of those bursts (i.e., the value ... </span><span style="background:none repeat scroll 0% 0% lime">TBC</span><span lang="EN-US"><u></u><u></u></span></p>
<p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><span style="font-family:Consolas" lang="EN-US"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:9pt;font-family:"Verdana","sans-serif"" lang="EN-US">*************************************************<br>
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<br></blockquote></div><br><br clear="all"><br>-- <br><div dir="ltr">__________________________________________________________<br>___________________________________________________________<br><br>Professor Wayne M. Getz<br>
A. Starker Leopold Professor of Wildlife Ecology<br>Department Environmental Science Policy & Management<br>130 Mulford Hall<br>University of California at Berkeley<br>CA 94720-3112, USA<br><br>Campus Visitors: My office is in 5052 VLSB<br>
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