On Thu, 28 Jul 2011, Jonathan Greenberg wrote:
Hi Dylan:
Thanks -- I'm a bit of a PostGIS noob so I ended converting it to a
normal point file with the XTools extension in Arc. ?I'm surprised
there is no support for this data type in any R package, since I would
think it is a fairly common type. ?Ah well!
Jonathan,
Not really, as this is the first time I can recall it being mentioned in 8
years. It is far from obvious what one could do with it that couldn't more
properly be done with a SpatialPointsDataFrame with a grouping factor. What
is the implied support of the data? What are the attributes attached to -
say var1 was observed at which of the member points? All of them
simultaneously? If they form a line or polygon, then support is clear(er),
but if a multipoint observation is better handled as described above, then
it should be. Support is absolutely crucial for clarity in analysis (and
visualization), I think.
Roger
PS: this is a similar case to that of the unusual M coordinate in some
shapefiles - if it cannot be shown how this relates consistently to support,
it shouldn't be admitted, I think. If we lose clear understanding of support
for observation attributes, we cease to be able to interact with
statisticians, and that interaction really matters.
--j
On Tue, Jul 26, 2011 at 2:28 PM, Dylan Beaudette
<dylan.beaudette at gmail.com> wrote:
Hi Jonathan,
My tool of choice for this operation is PostGIS. If you happen to have
a postgis db ready to go, simply import your problem file using the
postgis shapefile import tool and process there. Some tips here:
http://amercader.net/blog/2011/04/exploding-multigeometries-with-postgis
Cheers,
Dylan
On Tue, Jul 26, 2011 at 2:13 PM, Jonathan Greenberg
<greenberg at ucdavis.edu> wrote:
R-sig-geo'ers:
I have an ESRI shapefile which has multi-point geometry, and I'm
trying to get it into R for use with sp() and raster(). ?Using:
points=readOGR(dsn=getwd(),layer="tnf_sub_2_TreeDig_pts_110725_v02")
returns:
Error in readOGR(dsn = getwd(), layer =
"tnf_sub_2_TreeDig_pts_110725_v02", ?:
?Incompatible geometry: 4
In addition: There were 50 or more warnings (use warnings() to see the
first 50)
the warnings all say:
...
50: In readOGR(dsn = getwd(), layer =
"tnf_sub_2_TreeDig_pts_110725_v02", ?... :
?eType not chosen
What I really want is to, in the end, have a SpatialPointsDataFrame
where each multi-point feature is converted to individual points that
have the attribute of what multi-point feature it came from. ?What is
the best way to do this? ?I'm attaching the zipped shapefile to this
email (hopefully it won't get bounced).
--j
--
Jonathan A. Greenberg, PhD
Assistant Project Scientist
Center for Spatial Technologies and Remote Sensing (CSTARS)
Department of Land, Air and Water Resources
University of California, Davis
One Shields Avenue
Davis, CA 95616
Phone: 415-763-5476
AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307