Hi all.
Just
a short post to spread the announcement of the recent release of two
R packages: rpostgis (see also here) and RQGIS (see also here and here).
The first facilitates transfer between
PostGIS "Geometry" objects (stored in PostgreSQL databases)
and R spatial objects; the latter
establishes an interface between R and QGIS
and allows the
user to access the many
QGIS geoalgorithms from within R.
I
tested them briefly and I think they are very useful tools to perform
and simplify statistical and geo-statistical analyses in
archaeological contexts. Here I
present a quick example of usage.
Firstly I imported a set of
archaeological site-points stored in a PostgreSQL/PostGIS database.
That is very simple with rpostgis package: it's enough to create a
database connection (like in RpostgreSQL package) and launch the "pgGetGeom" function.
Then I
used RQGIS package to run (within R) the QGIS geoalgorithm that
builds a polygon from layer extent. After setting the same parameters
required by QGIS, the function "run_qgis" creates a red polygon
around the outermost points of my dataset.
Actually, must be careful to the version of QGIS we are using. With
2.14 there's no problem, but if you're using 2.16.1 or 2.16.2 (like
me) you must modify the QGIS file "AlgorithmExecutor.py" (path
for linux users should be: "/usr/share/qgis/python/plugins/processing/AlgorithmExecutor.py")
as described in the web page.
In the next future this problem should be correct by QGIS core
team.
At
the end I performed a specific point pattern analysis with the data
imported and created by
our two packages: in this example I calculated the Ripley's K
function (for an archaeological example see here)
in order to identify the distribution model
(random, regular or clustered) of my
archaeological sites.
In my
opinion these two new R packages make easier and faster the
traditional spatial analyses in R and facilitate a more virtuous
integration between GIS, geo-database and statistics.
Bye.
Denis
Francisci
No comments:
Post a Comment