#3184: v.ect.stats: errors in counts and statistics
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Reporter: veroandreo | Owner: grass-dev@…
Type: defect | Status: new
Priority: normal | Milestone: 7.2.0
Component: Vector | Version: svn-trunk
Keywords: v.vect.stats | CPU: x86-64
Platform: Linux |
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I am working with cases of a disease in Greece. So, I have points
(coordinates) and I need to get a count of those cases per municipality
and higher administrative units, i.e: NUTS. However, v.vect.stats gives
wrong counts. In, my case, I should have 615 cases and if I sum the cases
counted by v.vect.stats (using v.db.select mymap column=cases), I get 767.
In some polygons, it counts ok, in some it misses points, in others it
"invents" extra points.
I guess the whole problem is maybe related to the fact that Greece has so
many islands split in a much lower number of categories (i.e.: belonging
to a reduced number of administrative units), but I don't know.
Anyway, I attach a vector of polygons and a vector of points as an
example. They were created in NC demo location. Just unpack and run:
{{{
v.vect.stats -p points=points_test areas=areas_test method=average
points_column=value count_column=count stats_column=average
}}}
This is the output:
{{{
area_cat|count|average
1|3|5.5
2|0|null
3|6|11.3333333333333
3|0|null
6|2|10.5
}}}
Printing to stout gives two lines for cat 3, one with the right count, one
with 0. However, G7:v.db.select gives a different output:
{{{
v.db.select areas_test
cat|count|average
1|3|5.5
2|0|
3|0|
6|2|10.5
}}}
If you query the map from the GUI or display the attribute table, polygons
with cat 3 have 0 count (see attached screenshot).
Not only the count is wrong, but the average seems also weird. The three
points in the polygons with cat 1 have a value of 5, why would average be
5.5?
I'm running GRASS trunk r69699 under Fedora 24.
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Ticket URL: <https://trac.osgeo.org/grass/ticket/3184>
GRASS GIS <https://grass.osgeo.org>
