Questions tagged [near-neighbors]

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Time Complexity for Nearest Neighbor Searches in kd-trees

Nearest neighbor searches in kd-trees run in logarithmic time, as shown by Friedman et al. However, I have some difficulty to fully understand the proof. In order to calculate the average number of ...
1
vote
1answer
869 views

Simple k-nearest-neighbor algorithm for euclidean data with highly variable density?

An elaboration on this question, but with more constraints. The idea is the same, to find a simple, fast algorithm for k-nearest-neighbors in 2 euclidean dimensions. The bucketing grid seems to work ...
8
votes
1answer
169 views

Dynamic planar exact k-nearest neighbors for pathological data

What are the best known results for a data structure offering the following operations on sets of points in 2-dimensional euclidean space: $insert(x)$ $delete(x)$ $nearest(k,x)$ (where $k$ is an ...
9
votes
2answers
2k views

Calculating the distance to the kth nearest neighbor for all points in the set

For a machine learning application, my group needs to calculate the Euclidean distance to the $k$th nearest neighbor in a set $X$ for each $x \in (X \cup Y) \subset \mathbb R^d$ (for $d$ between 5 and ...
2
votes
1answer
644 views

What data structures exist for fast calculation of distances between multi-dimensional points

I'm writing a program that receives data over a network connection. Every data point is simply a 4 dimensional vertex, lets call the dimensions X,Y,Z,W. The values of each dimension are exponentially ...
4
votes
1answer
423 views

Does kd tree requires triangular inequality for finding k-nearest neighbors

I have 3-dimensional data I want to store in a kd-tree. Additionally I have a domain-specific distance function in this space for which I have a hard time to prove the triangular inequality. Here is ...
6
votes
3answers
290 views

Best algorithm for calculating lists of neighbours

Given a collection of thousands of points in 3D, I need to get the list of neighbours for each particle that fall inside some cutoff value (in terms of euclidean distance), and if possible, sorted ...
10
votes
4answers
838 views

Costs of performing approx. nearest neighbor search in a skip quadtree

NOTE: The question has been restated in my answers: Assuming now that we can find the lowest sibling ancestors in $O(1)$ time, can the ANN be really performed in $O(\log n)$? Quadtrees are efficient ...
1
vote
1answer
1k views

Compare similar N-Dimensional vector in a database

I want to compute Euclidian distance between similar vectors in a database (SQLite). So each column in the database is a value from my vector. The first problem appears, I have a large number of ...