[Numpy-discussion] computing average distance

Paul Rudin paul@rudin.co...
Sun Nov 2 23:52:30 CST 2008

Gael Varoquaux <gael.varoquaux@normalesup.org> writes:

> Hey Emmanuelle, ( :>)
> On Sun, Nov 02, 2008 at 08:39:39PM +0100, Emmanuelle Gouillart wrote:

Thanks both of you.

>    this will avoid what seems to be an error in Emmanuelle's answer. By
>    the way, I am not too sure why Paul has used a numpy.array here. For
>    this part of the code, it is not terribly usefull.

I'd used array because of what I do next. Having found the average
distance from the centre I want to scale the image so that the average
weight is about R/2, and then move the image so that it's centred around
the middle of the space. This is quite slow too...

scale_factor = (R/2)/av_dist

# scale so that our average distance from the centre is R/2
def transformer(point):
    return tuple(((numpy.array(point) - centre) * scale_factor)
                 + centre)

self.bits = scipy.ndimage.geometric_transform(self.bits, transformer)

# move so that we're centred in the middle of the voxelspace
self.bits = scipy.ndimage.shift(self.bits, midpoint-centre)

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