[GRASSLIST:3030] v.extract without centroids

Dear list,

I have two questions:

1) I imported an area shape with 6000 polygons in g57 and
there are 2 centroids missing. How can I find these two
centroids?

2) I used v.extract on this shape (with the 2 missing centroids).
v.extract in=SHAPE out=SHAPE2 type=area where='AREAQM>1'.

The areas geometry is extracted correctly but now all without centroid.
Is this because there were 2 missing in the beginning?

SHAPE
Number of nodes : 12171
Number of primitives: 15470
Number of points : 0
Number of lines : 0
Number of boundaries: 10777
Number of centroids : 4693
Number of areas : 4695
Number of isles : 1396
Number of areas without centroid : 2

SHAPE2 after using v.extract:
Number of nodes : 6602
Number of primitives: 7529
Number of points : 0
Number of lines : 0
Number of boundaries: 7529
Number of centroids : 0
Number of areas : 2300
Number of isles : 1373
Number of areas without centroid : 2300

thanks for help
  Otto

On Thursday 25 March 2004 13:36, Otto Dassau wrote:

Dear list,

I have two questions:

1) I imported an area shape with 6000 polygons in g57 and
there are 2 centroids missing. How can I find these two
centroids?

I believe that those 2 areas without centroids are slivers between
shape polygons.

2) I used v.extract on this shape (with the 2 missing centroids).
v.extract in=SHAPE out=SHAPE2 type=area where='AREAQM>1'.

Try type=area,centroid. This is not correct and it should be fixed,
type=area must export also centroids.

Radim

The areas geometry is extracted correctly but now all without centroid.
Is this because there were 2 missing in the beginning?

SHAPE
Number of nodes : 12171
Number of primitives: 15470
Number of points : 0
Number of lines : 0
Number of boundaries: 10777
Number of centroids : 4693
Number of areas : 4695
Number of isles : 1396
Number of areas without centroid : 2

SHAPE2 after using v.extract:
Number of nodes : 6602
Number of primitives: 7529
Number of points : 0
Number of lines : 0
Number of boundaries: 7529
Number of centroids : 0
Number of areas : 2300
Number of isles : 1373
Number of areas without centroid : 2300

thanks for help
  Otto

Radim Blazek schrieb:

On Thursday 25 March 2004 13:36, Otto Dassau wrote:
> Dear list,
>
> I have two questions:
>
> 1) I imported an area shape with 6000 polygons in g57 and
> there are 2 centroids missing. How can I find these two
> centroids?

I believe that those 2 areas without centroids are slivers between
shape polygons.

> 2) I used v.extract on this shape (with the 2 missing centroids).
> v.extract in=SHAPE out=SHAPE2 type=area where='AREAQM>1'.

Try type=area,centroid. This is not correct and it should be fixed,
type=area must export also centroids.

Hi Radim,

thank you for your hint:

I used:
v.extract in=SHAPE out=SHAPE2 type=area,centroid where='AREAQM>1'.

it exports areas _and_ the centroids, but now _all_ areas,
although I just want to export areas > 1 with centroid.

Number of nodes : 6765
Number of primitives: 7692
Number of points : 0
Number of lines : 0
Number of boundaries: 7529
Number of centroids : 163
Number of areas : 2300 -> should be 163 !
Number of isles : 1373
Number of areas without centroid : 2137

What can be done to solve this?

  thank you
   Otto

On Friday 26 March 2004 13:47, Otto Dassau wrote:

Radim Blazek schrieb:
> On Thursday 25 March 2004 13:36, Otto Dassau wrote:
> > Dear list,
> >
> > I have two questions:
> >
> > 1) I imported an area shape with 6000 polygons in g57 and
> > there are 2 centroids missing. How can I find these two
> > centroids?
>
> I believe that those 2 areas without centroids are slivers between
> shape polygons.
>
> > 2) I used v.extract on this shape (with the 2 missing centroids).
> > v.extract in=SHAPE out=SHAPE2 type=area where='AREAQM>1'.
>
> Try type=area,centroid. This is not correct and it should be fixed,
> type=area must export also centroids.

Hi Radim,

thank you for your hint:

I used:
v.extract in=SHAPE out=SHAPE2 type=area,centroid where='AREAQM>1'.

it exports areas _and_ the centroids, but now _all_ areas,
although I just want to export areas > 1 with centroid.

Number of nodes : 6765
Number of primitives: 7692
Number of points : 0
Number of lines : 0
Number of boundaries: 7529
Number of centroids : 163
Number of areas : 2300 -> should be 163 !
Number of isles : 1373
Number of areas without centroid : 2137

What can be done to solve this?

No idea, for me it works.

Radim