Hmm that's strange, I haven't seen that error. What version of shapely are
you using (I'm using 1.3.0). Also I'm on python 1.7.6.
Attaching the exact python script that I am running at my end.
I have also found that if I add small random numbers to each element of the
data array (gaussian random numbers of order 1e-2) then I do not get the
crash (and in fact I get the correct result), which suggests to me that
this is some instability/round-off issue.
Alex
On Mon, Apr 28, 2014 at 3:12 PM, Oleksandr Huziy <guziy.sa...@gmail.com>wrote:
> I get this error message when executing your code:
>
> ERROR:shapely.geos:TopologyException: depth mismatch at at
> 581037.39250326285 4509301.9737485535
>
>
> Have no idea what this means, but maybe you know))
>
> Cheers
>
>
> 2014-04-28 14:55 GMT-04:00 Alex Flint <alex.fl...@gmail.com>:
>
>> The following code produces an exception under shapely (python version)
>> 1.3.0
>>
>> import shapely.geometry
>> path = shapely.geometry.LineString([
>> [581037.19575668662, 4509299.98342364],
>> [580996.61134201661, 4509304.202782942],
>> [581037.19575668662, 4509299.98342364],
>> [581072.19594137045, 4509296.7024005251],
>> [581072.19594137045, 4509296.7024005251],
>> [581037.19575668662, 4509299.98342364]
>> ])
>> path.parallel_offset(2, shapely.geometry.JOIN_STYLE.mitre)
>>
>> The exception is:
>>
>> File
>> "/Users/alexflint/Code/wifi-localization/tools/localization/estimation/scripts/shapely_bug.py",
>> line 39, in <module>
>> linestring.parallel_offset(2, shapely.geometry.JOIN_STYLE.mitre)
>> File
>> "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/shapely/geometry/linestring.py",
>> line 114, in parallel_offset
>> bool(side == 'left')))
>> File
>> "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/shapely/geometry/base.py",
>> line 55, in geom_factory
>> raise ValueError("No Shapely geometry can be created from null
>> value")
>> ValueError: No Shapely geometry can be created from null value
>>
>> The points on the path above are actually very close to collinear, but my
>> understanding was that parallel_offset should work regardless. I have
>> attached a plot of the path itself.
>>
>> Any suggestions for what's going on here?
>>
>> Alex
>>
>>
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>>
>>
>
>
> --
> Sasha
>
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>
import shapely.geometry
path = shapely.geometry.LineString([
[581037.19575668662, 4509299.98342364],
[580996.61134201661, 4509304.202782942],
[581037.19575668662, 4509299.98342364],
[581072.19594137045, 4509296.7024005251],
[581072.19594137045, 4509296.7024005251],
[581037.19575668662, 4509299.98342364]
])
path.parallel_offset(2, shapely.geometry.JOIN_STYLE.mitre)
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