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I am trying to write code for Voronoi patches. This works fine with Matlab as seen below:

<!-- language: lang-Matlab -->
z = cat(2, x,y); 
[V, C] = voronoin(z);
for i = 1:length(C)
    if any( C{i} == 1)
        continue
    else
        Cnew = [Cnew, i];
    end
end

for i = 1:length(Cnew)
    xx = V( C{Cnew(i)} , 1);
    yy = V( C{Cnew(i)} , 2);
    disp(i), disp(xx), disp(yy)
    plot(xx,yy, 'Color', 'blue')
end

which is actually what I want!

However, since Matlab calls qhull, I wanted to use it directly, so that I can create a free version for my friends. So I used qhull directly from the commandline, and used its output to do the plotting. This is the result:

Now this is obviously wrong. So the relevant code for obtaining this is as follows:

The command that I use on the command line (for the same set of data points) is the following:

qvoronoi o QJ Fo < data.txt > output.txt

As can be seen, some the the vertices are not correct, although the majority of the vertices are ok ...

The relaxant part of the code used for this plot is the following:

for pD in pData:
    if 0 in pD: continue
    pD = pD + [pD[0]]
    x, y = np.array([vData[i] for i in pD]).T
    pl.plot(x,y, color='blue')
pl.show()

Here, pData are the "patch" information that looks like this:

In [6]: pData[:10]
Out[6]:
[[6, 312, 280, 228, 0, 163, 311],
 [4, 0, 228, 230, 229],
 [8, 0, 100, 101, 20, 21, 19, 70, 163],
 [5, 314, 281, 70, 163, 311],
 [4, 0, 18, 160, 229],
 [4, 282, 19, 70, 281],
 [4, 161, 157, 18, 160],
 [5, 103, 99, 101, 100, 102],
 [6, 101, 20, 76, 75, 37, 99],
 [6, 0, 100, 102, 41, 40, 356]]

While vData are the vertices which look like that:

In [7]: vData[:10]
Out[7]:
[[-10.101, -10.101],
 [475.0000000012008, 522.999999964199],
 [465.1459330246624, 450.7368421188263],
 [537.1737804542415, 426.2004572957462],
 [477.2870813371678, 434.0427631710093],
 [484.6180167742115, 54.98463685526782],
 [433.9793388408901, 439.3090909117672],
 [399.2310513506661, 466.2359413331789],
 [417.877358491973, 465.8773584984193],
 [461.9861308542621, 410.6663110455131]]

This information is obviously not correct. I am guessing that the problem is with the way in which I am calling qhull. Maybe I am not using the right flags? Can someone throw some light on the subject please??

Some specifications about the system I am working on: Windows 7 Matlab version R2010A Python 2.7

I actually use Python's subprocess module to run a DOS shell command to get the values directly from Qhull. That part is as follows: 

# Execute qvoronoi to get the vertices and patches
p = subP.Popen('bin\qvoronoi o %s < %s'%(params, fileName), \
                shell=True, \
                stdout=subP.PIPE, \
                stderr=subP.STDOUT)
lines  = p.stdout.readlines()
retval = p.wait()

However, this part is working properly. I have already verified this.

Note: I cannot post images. Apparently this is a "reputation" thing. If you want to see the images, please feel free to ask ...

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1 回答 1

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事实证明，最新版本的 SciPy 在scipy.spatial 模块中包含 voronoi 。正如文档所说，它是 0.12.0 版中的新功能。现在您可以下载最新版本的 Scipy 并直接使用此功能。快速说明：这将返回一些带有 -1 的顶点以表示无限顶点，并且可能返回空数组，这有点烦人。

不幸的是，我仍然不知道如何正确使用 Qhull。

于 2013-12-26T23:36:41.440 回答