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<p>Hi Michelle,</p>
<p>Good question. The short answer is that yes all hulls have a time
stamp associated with them (specifically the timestamp of the
'parent point'), regardless of the value of s (which only affects
which other points are considered nearest neighbors). <br>
</p>
<p>Whether it makes sense or not to pair-up hulls from different
individuals based on the time stamp of the parent point, when hull
construction does not take time into consideration, is a good
question. When s>0, one can say with their head held high that
the points that compose the hull are in some sense local in both
time in space. In that case it's reasonable to compare two
space-time hulls from different individuals at the same time, and
take their physical distance apart as some kind of association
metric at that moment in time. <br>
</p>
<p>When time is not included in hull construction, the meaning of a
hull is more akin to density of usage over the entire sampling
interval. In that case, the time stamp of the parent point doesn't
signify any particular characteristic at that moment in time
except maybe to say at that specific moment the individual was in
a high density hull or a low density hull. That might have some
significance if you see high density hulls occurring during a
certain time of the day or part of the season. Pairing space-only
hulls from two individuals at the same time might allow you to say
whether or not the two individuals tended to be in high density or
low density hull at the same time, but it wouldn't tell you much
about their association at that particular time (I think). <br>
</p>
<p>That being said, you could incorporate another hull metric
'tspan' (time span of the nearest neighbors) to measure the time
span of the nearest neighbors (regardless of s), and use tspan to
compare the window of time that two two time-matched hulls
represent. If the hulls for individual A and individual B have a
similar distribution of tspan, you might be able to argue that
time-paired hulls are a measure of dynamic association at the
scale of tspan. <br>
</p>
<p>Cheers,<br>
Andy</p>
<p><br>
</p>
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<div class="headerdisplayname" style="display:inline;">Subject:
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Calculating temporally overlapping hulls with s=0, can it be
done?</td>
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<div class="headerdisplayname" style="display:inline;">From:
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Michelle Pretorius <a class="moz-txt-link-rfc2396E" href="mailto:PRTMIC015@myuct.ac.za"><PRTMIC015@myuct.ac.za></a></td>
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<div class="headerdisplayname" style="display:inline;">Date:
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5/7/2021, 3:38 AM</td>
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<div class="headerdisplayname" style="display:inline;">To: </div>
<a class="moz-txt-link-rfc2396E" href="mailto:tlocoh-info@lists.r-forge.r-project.org">"tlocoh-info@lists.r-forge.r-project.org"</a>
<a class="moz-txt-link-rfc2396E" href="mailto:tlocoh-info@lists.r-forge.r-project.org"><tlocoh-info@lists.r-forge.r-project.org></a></td>
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<p class="MsoNormal">Hi all, </p>
<p class="MsoNormal">I would like to calculate <span
style="color:black;background:white;mso-fareast-language:EN-GB">
hull metrics for pairs of temporally overlapping hulls of
two individuals (using `lhs.to.add` from the `tlocoh.dev`
package). However, I have used s=0 for both individuals
(after following the cross-validation methods set out by <a
href="https://movementecologyjournal.biomedcentral.com/articles/10.1186/s40462-017-0110-4">
Dougherty et al. (2017)</a>), and thus the hulls were
constructed from the closest points in space only. </span><span
style="color:black;mso-fareast-language:EN-GB">Do hulls
still have times associated with them even if they are
formed with s = 0?</span><span
style="mso-fareast-language:EN-GB"></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-GB">Using
the `lhs.to.add` and `lhs.to.stats` functions I do <i>technically</i>
get a result (i.e., there are no errors), but I am wondering
if this is theoretically sound?</span></p>
<p class="MsoNormal"><span
style="color:black;mso-fareast-language:EN-GB">Thank you in
advance for any help/advice you can provide.</span></p>
<p class="MsoNormal"><span
style="color:black;mso-fareast-language:EN-GB">Best,<br>
Michelle</span></p>
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