[GRASS-user] Median filtering time series in time only

[Stefan Blumentrath]

Hei,

Maybe a two-step approach with t.rast.aggregate and t.rast.mapcalc could work?
In t.rast.aggregate you define the granularity as e.g. 48 days if you want to get a running median over three time steps of a 16 days time series.

If you want to do it in one go (which would be understandable for heavy time series), I assume t.rast.algebra is your best bet. Here is an example on how to add a new function: https://github.com/OSGeo/grass/pull/905/files to the module (which admittedly is quit complex) (the d-falg helps with testing under development).
You may have to invent a distinct pattern for aggregate functions from r.mapcalc…

Cheers
Stefan


From: grass-user <grass-user-bounces at lists.osgeo.org> On Behalf Of Veronica Andreo
Sent: torsdag 28. januar 2021 16:43
To: Nikos Alexandris <nik at nikosalexandris.net>
Cc: grass-user @lists.osgeo.org <grass-user at lists.osgeo.org>
Subject: Re: [GRASS-user] Median filtering time series in time only



El jue, 28 ene 2021 a las 0:05, <nik at nikosalexandris.net<mailto:nik at nikosalexandris.net>> escribió:

On 2021-01-27 16:59, Veronica Andreo wrote:

Both r.series and t.rast.series will estimate the median per pixel in time (either for the whole series or the time period you want). Would it be possible then with so e sort of special for cycle?

Sorry, I didn't pay attention. Reading more carefully.
Indeed, r.series (t.rast.series) do the median. But they will just create a single pixel for each pixel time series.
Then, as you write, it would take to hack-around a way to iterate over a given time series at the desired (number of) intervals, then compile a new time series.

What is the 'e sort' part?
Did you mean to type 'with some sort of...'?
And what does the 'cycle' refer to?

Sorry Nikos! I was writing from my phone and it gets messy sometimes. The intended sentence was: "Would it be possible then with some sort of special `for loop`?"


Thanks, Nikos

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