nearest-neighbor

I'm beginning to learn Python coming from a C++ background. What I am looking for is a quick and easy way to find the closest (nearest neighbor) of some multidimensional query point in an 2D (numpy) array of multidimensional points (also numpy arrays). I know that scipy has a k-d tree, but I don't think this is what I want. First of all, I will be changing the values of the multidimensional points in the 2D array. Secondly, the position (coordinates) of each point in the 2D array matters as I will also be changing their neighbors. I could write a function that goes through the 2D array and

Is anyone aware of a nearest neighbor algorithm implemented in Python that can be updated incrementally? All the ones I've found, such as this one , appear to be batch processes. Is it possible to implement an incremental NN algorithm? RandomGuy I think the problem with incremental construction of a KD-tree or KNN-tree is, as you've alluded to in a comment, that the tree will eventually become unbalanced and you can't do simple tree rotation to fix balance problems and keep consistency. At the minimum, the re-balancing task is not trivial and one would definitely not want to do it at each

I need to have an image render with nearest-neighbor resizing and not the bicubic way that is currently used. I currently use the following: ms-interpolation-mode: nearest-neighbor; image-rendering: -moz-crisp-edges; This works in IE and Firefox, but not in Chrome and Safari. Are there any webkit alternatives or any other way to achieve this effect? thirtydot Edit: It's now possible with image-rendering: -webkit-optimize-contrast; . https://developer.mozilla.org/en-US/docs/CSS/image-rendering#Examples This doesn't work in current versions of Chrome, here are some useful links: http:/

I'm working with PostgreSQL 9 and I want to find the nearest neighbor inside table RP for all tuples in RQ , comparing the dates ( t ), but I get this error: ERROR: subquery in FROM cannot refer to other relations of same query level using this query: SELECT * FROM RQ, (SELECT * FROM RP ORDER BY ABS(RP.t - RQ.t) LIMIT 1) AS RA RQ.t in subquery seems to be the problem. How can I avoid this error? How can I get access from subquery to RQ ? Erwin Brandstetter Update: LATERAL joins allow that and were introduced with Postgres 9.3. Details: What is the difference between LATERAL and a subquery in

In a cubic box I have a large collection points in R^3. I'd like to find the k nearest neighbors for each point. Normally I'd think to use something like a k-d tree, but in this case I have periodic boundary conditions. As I understand it, a k-d tree works by partitioning the space by cutting it into hyper planes of one less dimension, i.e. in 3D we would split the space by drawing 2D planes. For any given point, it is either on the plane, above it, or below it. However, when you split the space with periodic boundary conditions a point could be considered to be on either side! What's the most

Given a quaternion value, I would like to find its nearest neighbour in a set of quaternions. To do this, I clearly need a way to compare the "distance" between two quaternions. What distance representation is needed for such a comparison and how is it computed? Thanks, Josh Olhovsky Is your quaternion just a point in 3D space with an orientation? Then the distance between two quaternions x1,y1,z1,w1 and x2,y2,x2,w2 is given by: distance = sqrt((x1-x2)^2 + (y1-y2)^2 + (z1-z2)^2) , assuming that the w component is used for orientation. I.e. this is the same as the distance between two 3D points