On Thu, 25 Aug 2011, Karl Ove Hufthammer wrote:
Dear list members,
Is it possible to define which FID values should be used when
saving a SpatialPointsDataFrame to a GML files using writeOGR
(rgdal package)?
The FID values are stored as <ogr:layername fid="F0"> (and F1,
F2, …). If I insert a new row in the SPDF, most features change
their FID, which creates much unneccessary noise in our VCS,
so I would like to use an already existing ID as the FID.
I have tried change both the row.names and adding columns named
‘fid’ and ‘gml_id’, the writeOGR still only uses F0, F1, … as
the FIDs.
No FID is set in writeOGR() in the underlying C++ function writeOGR(). One
could be set, but only as unique integers >= 0, not as the row.names()
which are strings. The result is that default FID are written. It would be
possible to modify the function to add integer FID, I think, but they
would have to be valid unique integers. I think that what gets
written from there depends on the driver internals, which the
function does not reach. Would this help? Patches welcome!
Best wishes,
Roger
--
Karl Ove Hufthammer
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--
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
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