In my opinion the first item on the agenda should be to
get good documentation in place including many examples.
On 3/16/07, Edzer J. Pebesma <[EMAIL PROTECTED]> wrote:
> Although I'm interested many of the issues below, and also feel the
> attraction of the develop-it-ourself, my personal agenda
Although I'm interested many of the issues below, and also feel the
attraction of the develop-it-ourself, my personal agenda is a bit more
modest. Once we start with GEOS support (an idea mentioned every 6
months on this list), the next thing we need for dealing with huge or
massive data sets i
On 3/16/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
>
>
> > My OSGeo summer of code idea is to link the BGL to postgis. I wasn't
> > originally thinking about topology per se, but it would achieve much the
> > same thing.
>
>
> I've thought a bit about this project, too, as it butts up against
> My OSGeo summer of code idea is to link the BGL to postgis. I wasn't
> originally thinking about topology per se, but it would achieve much the
> same thing.
I've thought a bit about this project, too, as it butts up against some of
my own work.
My experience with graph libraries has not
On Fri, 16 Mar 2007 [EMAIL PROTECTED] wrote:
> The thread below and many others in R-sig-Geo raise questions about
> future directions. In reinventing GIS there are a whole list of
> capabilities and functions that would be helpful. Some that I have
> noticed include,
>
> Topological representa
Denis,
I was just about to reply to Nicholas that my ideal solution would be
to build a graph data structure linking adjacent elements and find the
the hull that way -- I think you saw the solution before I did. (I'm
starting to grok that all of this is already well known in the vector
GIS world w
Hi Tim,
Now I think I get it. What about the following:
1) threshold based on your qvalues
2) find all disconnected sets
3) For each disconnected set
a) find the convex hull of the hexagon centers, this should be
equivalent to the
the convex hull of the hexagons themselves (convexity of
The thread below and many others in R-sig-Geo raise questions about
future directions. In reinventing GIS there are a whole list of
capabilities and functions that would be helpful. Some that I have
noticed include,
Topological representation to enable
Planar enforcement of boundary integr
Ya, there can be pretty arbitrary holes. The situation is a large
hexagonal lattice where some fraction of cells have q-values < 0.05.
Now draw lines around those cells following the hexagonal edges, but
omitting any interior arcs. I can send you an example solution. The
images are bit big for the
Just found out a little about this in ArcGIS (ArcMap), version 9.1.
Yes, apparently with large datasets, the "natural breaks" classification
(and maybe others like quantile) does sample. However, it is possible
to change the sample size by clicking the "Sampling" button in the
Classification windo
Hi Tim,
You could compute the convex hull first, and then iterate from points
on the convex hull. That should be much faster already, especially since
hexagons are convex and the perimeter will be locally convex around all
the
points touching the convex hull. You could do a variation
of the "monoto
On Fri, 16 Mar 2007, Hervé Polesi wrote:
> Hi!
>
> Working on a litle datebase (903 lines) I notice a difference between
> the result of classInterval(style="fisher") and the natural breaks
> proposed by ArcView GIS (3.2).
> I read that ArcView works on a sample of data. Is it right ? May it
>
Hi Nic,
The convex hull would be fast and easy to compute (there's existing
code in R). I want the ordinary hull which is the set of arcs forming
the perimeters (inside and out). My crude and very slow solution was
to convert all the polygons (in this case hexagons on a lattice) into
their constit
Hi Tim,
I am not quite sure what you are getting at here. Do you want to
intersect
polygons and then select the set of lines that form the outer perimeter?
Do you wan the convex hull of a set of polygons. I guess I have been out
of the
GIS world to long. It seems to me that this would be something
Hi!
Working on a litle datebase (903 lines) I notice a difference between
the result of classInterval(style="fisher") and the natural breaks
proposed by ArcView GIS (3.2).
I read that ArcView works on a sample of data. Is it right ? May it
cause a significative difference ?
Greetings from Stra
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