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sftime #1

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edzer opened this issue Oct 1, 2019 · 4 comments
Open

sftime #1

edzer opened this issue Oct 1, 2019 · 4 comments

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@edzer
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edzer commented Oct 1, 2019

@luukvdmeer following up on our workshop during the OpenGeoHub summer school, I started a fresh repo for sf time objects. It's pretty empty still; for initial support we can think of methods for package gstat (all *ST functions; @BenGraeler) and for st_join methods with stars objects; see also appelmar/gdalcubes#26 for sampling a data cube along a trajectory.

@luukvdmeer
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Great! For me mainly the st_join method with stars objects looks very interesting and fits nice into the work I am doing on data cubes now in Salzburg. I would like to work on that as a start!

Just to make clear what your view on the scope of the package is (I know this is just a start and it might change over time):

  • As I understood, we are now mainly looking for a 'modern' alternative for what used to be the STIDF class in spacetime, since stars is already suitable for the STFDF and STSDF classes, and trajectories handles the STTDF class?
  • This includes finding ways to represent both time instances and (open and closed) time intervals.
  • And - on the long term - implementing temporal predicates (https://www.mdpi.com/data/data-04-00086/article_deploy/html/images/data-04-00086-g001.png), similar to the spatial predicate functions in sf?

@edzer
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edzer commented Oct 2, 2019

Yes; leaving trajectories on the side, for now, this is for time-stamped features.

Currently, time is a time stamp only; for Date one could interpret this as a "full day" (left-close, right-open), for POSIXct it is really a time instance IMO. If we want to represent time intervals, we need a class for this, I would take a list column with length two POSIXct values representing a single left-closed right-open interval: [from, to), nothing else. stars already has the ability to represent time as intervals. One could go all the way and allow a non-negative even number of values, indicating 0 or more intervals (0 for the missing interval).

Starting with st_join would be good, ignoring intervals in sftime objects first.

@bniebuhr
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Hi,

I've just found about this sftrack package: https://mablab.org/sftrack/
You may probably know, but I guess some parallels may be good!

@edzer
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edzer commented Nov 24, 2020

Thanks for reminding! Yes, coercion methods from and to sftrack seem to be trivial and useful.

@henningte henningte mentioned this issue Dec 19, 2021
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henningte added a commit that referenced this issue Apr 3, 2022
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