[SciPy-User] Mistake in the scipy-wiki/cookbook/KDTree
Gero Putzar
gputzar@beckarndt.com...
Wed Mar 9 22:55:47 CST 2011
Preferably to Mike Toews or whoever supplied this wiki page.
Hi,
first: Thank you very much for putting this explanatory code into the wiki.
I think there is a minor mistake in the code displayed on
http://www.scipy.org/Cookbook/KDTree in the subsection "Searching a
kd-tree", function radius_search(): Within this function the radius is
supplied as second argument to the function intersect(). But intersect()
expects the square of the radius as argument.
I suggest the following modified version. Note that this modified version
now returns the square distances very much like the corresponding knn_search
function above.
--- snip ---
def radius_search(tree, datapoint, radius):
""" find all points within radius of datapoint """
stack = [tree[0]]
inside = []
radsq = radius**2
while stack:
leaf_idx, leaf_data, left_hrect, \
right_hrect, left, right = stack.pop()
# leaf
if leaf_idx is not None:
param=leaf_data.shape[0]
distsq = ((leaf_data -
datapoint.reshape((param,1)))**2).sum(axis=0)
near = numpy.where(distsq<=radsq)
if len(near[0]):
idx = leaf_idx[near]
distsq = distsq[near]
inside += (zip(distsq, idx))
else:
if intersect(left_hrect, radsq, datapoint):
stack.append(tree[left])
if intersect(right_hrect, radsq, datapoint):
stack.append(tree[right])
return inside
--- snap ---
I did not test this modification nor the original code. And I might be wrong
all together, of course.
Please cc directly to me if you want an answer because I'm not subscribed to
the list.
Thanks, kind regards,
Gero.
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