[GRASS-dev] [bug #4794] (grass) r.thin

[Markus Neteler via RT]

Hi,

r.thin works (in GRASS 6.1-CVS). Quick test:

GRASS 6.1.cvs (spearfish60): > g.region -dp
projection: 1 (UTM)
zone:       13
datum:      nad27
ellipsoid:  clark66
north:      4928010
south:      4913700
west:       589980
east:       609000
nsres:      30
ewres:      30
rows:       477
cols:       634

r.thin fields out=fields_skeleton
File fields -- 477 rows X 634 columns
Bounding box:  l = 3, r = 635, t = 2, b = 468
   Pass number 1
        Deleted 5632  pixels
   Pass number 2
...
   Pass number 81
        Deleted 0  pixels
Thinning completed successfully.
Output file 477 rows X 634 columns
Window 477 rows X 634 columns

d.mon x0
d.rast fields_skeleton
# -> looks ok, no data are present

r.univar fields_skeleton
 100%
total null and non-null cells: 302418
total null cells: 299926  <-- no data are there !

Of the non-null cells:
----------------------
n: 2492
minimum: 1
maximum: 63
range: 62
mean: 44.7364
standard deviation: 21.6878
variance: 470.363
variation coefficient: 48.4792 %
sum: 111483

I suspect that the original map doesn't have NULL where
you think they should be. You can verify it with d.what.rast.

I  don't see a problem in r.thin (note that we fixed it in
April):
2006-04-04 17:07  markus
        * main.c: increased to 200 iterations default
2006-04-04 17:06  markus
        * thin_lines.c: fixed max iterations
2006-04-04 16:48  markus
        * local_proto.h, main.c, thin_lines.c: added iterations parameter.
        Added exit error message if failure. Fixed wording. Increased
        default iterations

Markus

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