[pdal] pdal.pipeline.array to 2D np.ndarray

[Lothar Ulferts]

Hy,

I want to transform the points of multiple LAS files from cartesian 
coordinates to polar coordinates. The transformation is done with numpy 
in a two-dimensional /numpy.ndarray/.

But how do I get a 2D numpy.ndarray from the data of the PDAL pipeline 
(in the PDAL Python example the /pipeline.arrays/ )? From the PDAL 
Python example I changed the JSON expression:

pipe_reader = """
{
   "pipeline":[
     {
       "type":"readers.las",
       "filename":"%s"
     }
   ]
}
}"""%lasinput

/pipeline.arrays/ does not return an array, but a /list/ containing a 
one-dimensional /numpy.ndarray/. Each row of this array is a 
/numpy.void/ with the values of a point. My current solution is a 
listcomprehension:

arr_voids = arrays[0]
points = np.array([list(i) for i in arr_voids], dtype= arr_voids.dtype)

This way is too slow, too memory intensive  and not a "numpyical-way". 
But how do I get there with numpy or pdal? Perhaps I‘ve already chosen 
the wrong approach?

Thanks!
Lothar
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