matplotlib-users

Re: [Matplotlib-users] matplotlib pnpoly-example-results-in-error

[algotr8der <alg...@gm...>]

I tried to execute the following code:

http://matplotlib.org/faq/howto_faq.html#test-whether-a-point-is-inside-a-polygon

However I get errors I describe here:

http://stackoverflow.com/questions/16452509/matplotlib-pnpoly-example-results-in-error

>>>import numpy as np
>>>import matplotlib.nxutils as nx
>>>verts = np.array([ [0,0], [0, 1], [1, 1], [1,0]], float)
>>>nx.pnpoly(0.5, 0.5, verts)

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "C:\Python27\lib\site-packages\matplotlib\nxutils.py", line 26, in
pnpoly
    return p.contains_point(x, y)
  File "C:\Python27\lib\site-packages\matplotlib\path.py", line 289, in
contains_point
    transform = transform.frozen()
AttributeError: 'float' object has no attribute 'frozen'

>>>nx.pnpoly(0.5, 1.5, verts)

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "C:\Python27\lib\site-packages\matplotlib\nxutils.py", line 26, in
pnpoly
    return p.contains_point(x, y)
  File "C:\Python27\lib\site-packages\matplotlib\path.py", line 289, in
contains_point
    transform = transform.frozen()
AttributeError: 'float' object has no attribute 'frozen'

Apparently, nxutils is deprecated, which to me means it should still work
but a user on stackoverflow pointed out that there may be some code rot.
That said, the documentation on matplotlib.path.Path.contains_point is weak
(see below). Does anyone have an example of how I can do the exact same
thing in the code in the howto_faq but using the suggested function
(contains_point)?

http://matplotlib.org/1.2.1/api/path_api.html?highlight=contains_point#matplotlib.path.Path.contains_point

contains_point(point, transform=None, radius=0.0)

    Returns True if the path contains the given point.
    If transform is not None, the path will be transformed before performing
the test.
    radius allows the path to be made slightly larger or smaller.

contains_points(points, transform=None, radius=0.0)

    Returns a bool array which is True if the path contains the
corresponding point.
    If transform is not None, the path will be transformed before performing
the test.
    radius allows the path to be made slightly larger or smaller.






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Re: [Matplotlib-users] matplotlib pnpoly-example-results-in-error

[Nicolas R. <Nic...@in...>]

From the matplotlib page, you can reach:
http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html

and just translates the function:

def inside_polygon(p, vertices):
    vx,vy = vertices[:,0], vertices[:,1]
    x,y = p
    c = 0
    j = len(vertices)-1
    for i in xrange(len(vertices)):
        if( ((vy[i] > y) != (vy[j] > y)) and (x < (vx[j]-vx[i]) * (y-vy[i]) / (vy[j]-vy[i]) + vx[i]) ):
            c = 1-c
        j = i
    return c

Of course this would be slower than the corresponding C implementation.

Nicolas


On May 9, 2013, at 21:55 , algotr8der wrote:

> I tried to execute the following code:
> 
> http://matplotlib.org/faq/howto_faq.html#test-whether-a-point-is-inside-a-polygon
> 
> However I get errors I describe here:
> 
> http://stackoverflow.com/questions/16452509/matplotlib-pnpoly-example-results-in-error
> 
>>>> import numpy as np
>>>> import matplotlib.nxutils as nx
>>>> verts = np.array([ [0,0], [0, 1], [1, 1], [1,0]], float)
>>>> nx.pnpoly(0.5, 0.5, verts)
> 
> Traceback (most recent call last):
>  File "<console>", line 1, in <module>
>  File "C:\Python27\lib\site-packages\matplotlib\nxutils.py", line 26, in
> pnpoly
>    return p.contains_point(x, y)
>  File "C:\Python27\lib\site-packages\matplotlib\path.py", line 289, in
> contains_point
>    transform = transform.frozen()
> AttributeError: 'float' object has no attribute 'frozen'
> 
>>>> nx.pnpoly(0.5, 1.5, verts)
> 
> Traceback (most recent call last):
>  File "<console>", line 1, in <module>
>  File "C:\Python27\lib\site-packages\matplotlib\nxutils.py", line 26, in
> pnpoly
>    return p.contains_point(x, y)
>  File "C:\Python27\lib\site-packages\matplotlib\path.py", line 289, in
> contains_point
>    transform = transform.frozen()
> AttributeError: 'float' object has no attribute 'frozen'
> 
> Apparently, nxutils is deprecated, which to me means it should still work
> but a user on stackoverflow pointed out that there may be some code rot.
> That said, the documentation on matplotlib.path.Path.contains_point is weak
> (see below). Does anyone have an example of how I can do the exact same
> thing in the code in the howto_faq but using the suggested function
> (contains_point)?
> 
> http://matplotlib.org/1.2.1/api/path_api.html?highlight=contains_point#matplotlib.path.Path.contains_point
> 
> contains_point(point, transform=None, radius=0.0)
> 
>    Returns True if the path contains the given point.
>    If transform is not None, the path will be transformed before performing
> the test.
>    radius allows the path to be made slightly larger or smaller.
> 
> contains_points(points, transform=None, radius=0.0)
> 
>    Returns a bool array which is True if the path contains the
> corresponding point.
>    If transform is not None, the path will be transformed before performing
> the test.
>    radius allows the path to be made slightly larger or smaller.
> 
> 
> 
> 
> 
> 
> --
> View this message in context: http://matplotlib.1069221.n5.nabble.com/re-matplotlib-pnpoly-example-results-in-error-tp41028.html
> Sent from the matplotlib - users mailing list archive at Nabble.com.
> 
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Re: [Matplotlib-users] matplotlib pnpoly-example-results-in-error

[Cameron H. <cam...@gm...>]

On 2013-05-09, at 3:55 PM, algotr8der <alg...@gm...> wrote:

> Apparently, nxutils is deprecated, which to me means it should still work
> but a user on stackoverflow pointed out that there may be some code rot.
> That said, the documentation on matplotlib.path.Path.contains_point is weak
> (see below). Does anyone have an example of how I can do the exact same
> thing in the code in the howto_faq but using the suggested function
> (contains_point)?


from matplotlib.path import Path
path = Path(polygonVerts)
isInside = path.contains_point(point)


--
Cameron Hayne
cam...@gm...