[GRASS-user] Attribute transfer from one table to another based on position of vector items

[Michael Perdue]

Thanks Daniel,

Unfortunately it doesn't work the way I need it to. It looks like v.what.vect uploads the first (or last) feature that it finds in "qmap" to "input". I need the values from every feature. Or better yet, the average of those values.

Cheers,

Mike

On 2012-06-09, at 2:50 AM, Daniel Lee wrote:

> Hi Mike,
> 
> Couldn't you use v.what.vect to upload the values from the lines to the points? They're collocated, right?
> 
> Best,
> Daniel
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> 
> 2012/6/9 Michael Perdue <michael_perdue at yahoo.ca>
> I have a similar goal, but the solution in the case below will not work for me.
> 
> I have three points A,B & C that I have linked together through Delaunay triangulation;
> 
>        A
>        /\
>       /  \
>      /    \
>     /      \
>    /        \
>   /          \
>  /____________\
> B              C
> 
> I want to create a new attribute for each point that is the average of the length of all the lines attaching each point to it's neighbours.
> So if;
> B->A = 1.0m
> A->C = 0.8m
> C->B = 0.6m
> 
> Then
> A = (1.0m + 0.8m) = 0.9m
> B = (1.0m + 0.6m) = 0.8m
> C = (0.6m + 0.8m) = 0.7m
> 
> Creating the Delaunay triangles and uploading the length of each face is easy, but I'm not entirely clear on how to relate the length of those vectors back to the points they were derived from. Any help would be greatly appreciated.
> 
> Cheers,
> 
> Mike
> 
> 
> On 2012-06-08, at 11:10 AM, Markus Metz wrote:
> 
>> On Fri, Jun 8, 2012 at 2:25 PM, Jaromír Kamler <kamler at centrum.cz> wrote:
>>> Hi,
>>> 
>>> I have two vectors imported from SHP. One contains lines (areas), which
>>> represents sites and in other are texts with cost of sites. I imported them
>>> to GRASS. Texts with costs of ground are now points with cost in attribute
>>> table and I turned circuid lines to the areas with centroids.I need copy
>>> costs from attribute table of costs to the attribute table of sites vector.
>>> I have no key for connection of this tables. Only one "key" is their
>>> position, because points with cost attribute are above corresponding areas.
>>> One point with cost of ground is above one area. How get cost of
>>> corresponding point to the corresponding attribute of ground? I do not see
>>> any simple possibility.
>> 
>> If both vectors are available as shapefiles, you could put the two
>> shapefiles into one directory (with no other shapefiles in it) and
>> then try something like
>> 
>> v.in.ogr dsn=/path/to/folder/with/shapefiles/ type=boundary,centroid
>> 
>> With type=boundary,centroid, lines will be converted to boundaries and
>> points to centroids. Attributes attached to sites (points) will now be
>> attached to areas, nothing else to do.
>> 
>> Markus M
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> 
> 
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