write.tgrass (spacetime) does not create init.txt
Hi Edzer, sorry for the delay. 2014-07-13 18:11 GMT+02:00 Edzer Pebesma <edzer.pebesma at uni-muenster.de>:
spacetime::write.tgrass (as it is on github) now writes init.txt, hopefully correct. I took examples from https://www-pool.math.tu-berlin.de/~soeren/grass/ , and used file precipitation_1950_2013_yearly_mm.tar.gz. In this file, init.txt has quite different content from that you describe below:
Oh, yes, sorry, i explained only the most basic file format. The keywords "stds_type" and "format" are by default "strds" and "GTiff" and can therefor be omitted in your case. But they have to be set in case of stvds and other data formats than geotiff. For raster data only GTiff, AAIGrid and the native tar-gzipped GRASS data formats are supported.
stds_type=strds format=GTiff temporal_type=absolute semantic_type=mean number_of_maps=63 north=75.5 south=25.25 east=75.5 west=-40.5 Does tgrass depend on knowing "relative_time_unit"?
TGRASS depends on relative time unit in case of relative time. Hence if you write time like 1,2,3,4, ... , 100 then you have to specify the unit of them. The relative time unit is not needed in case of calendar time, since only Gregorian time is supported.
I could write a function that write "years" when the number of days between time stamps is 356 or 366, and act similarly for "months" (28, 29, 30 or 31), but this is somewhat messy of course, and things get worse in case of daylight saving time and monthly data... Suggestions welcome!
How does R implements the concept of relative time, hence time without an absolute reference? Best regards Soeren
On 07/07/2014 06:57 PM, S?ren Gebbert wrote:
Hi, init.txt has the following content: temporal_type=absolute semantic_type=mean relative_time_unit=years number_of_maps=61 north=75.5 south=25.25 east=75.5 west=-40.5 The spatial extent is ignored while importing, but the temporal type, semantic type (still a dummy in TGRASS) and the number of maps must be provided. The relative time unit is mandatory if the dataset has relative time, otherwise it can be left out. I noticed that the reader expects always absolute time, is it possible to support relative time as well? Best regards Soeren 2014-07-07 18:46 GMT+02:00 Edzer Pebesma <edzer.pebesma at uni-muenster.de>:
Thanks for the clear report, Veronica. Soeren (Cc:), do you know where we can find a description of the requirements, or examples, of the init.txt file? On 07/07/2014 06:31 PM, Veronica Andreo wrote:
Hi list
I'm using R to run some processing over a spatio-temporal raster dataset
coming from GRASS. The workflow is as follows:
1. Export all my images from GRASS with t.rast.export
2. Import them as a raster stack in R with read.tgrass
3. do the processing... which implies converting the rasterstack into a
matrix, transposing and running dineof
4. create the rasterstack again, add the time with setZ
5. export with write.tgrass (which only seems to work for RasterStack and
not for STFDF, i tried both ways)
6. and import to grass again...
here is where I get the error since an init.txt file with the following
information is needed but it's not created by write.tgrass...
stds_type=strds
format=GTiff
temporal_type=absolute
semantic_type=mean
number_of_maps=
north=
south=
east=
west=
There are of course some workarounds but it would be nice -and much more
straightforward- that the function which is intended to provide interface
between R and T-GRASS, already does the job itself :)
Thanks much!
Best,
Vero
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-- Edzer Pebesma Institute for Geoinformatics (ifgi), University of M?nster Heisenbergstra?e 2, 48149 M?nster, Germany. Phone: +49 251 83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAC227795
-- Edzer Pebesma Institute for Geoinformatics (ifgi), University of M?nster Heisenbergstra?e 2, 48149 M?nster, Germany. Phone: +49 251 83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAC227795