the maximum number of nearest neighbors to search. The default value
is set to 10.
Details
The cover tree is O(n) space data structure which allows us to answer queries
in the same O(log(n)) time as kd tree given a fixed intrinsic dimensionality.
Templated code from http://hunch.net/~jl/projects/cover_tree/cover_tree.html is used.
The kd tree algorithm is implemented in the Approximate Near Neighbor (ANN) C++ library (see http://www.cs.umd.edu/~mount/ANN/).
The exact nearest neighbors are searched in this package.
The CR algorithm is the VR using distance 1-x'y assuming x and y are unit vectors.
The brute algorithm searches linearly. It is a naive method.
Value
a list contains:
nn.index
an n x k matrix for the nearest neighbor indice.
nn.dist
an n x k matrix for the nearest neighbor Euclidean distances.
Author(s)
Shengqiao Li. To report any bugs or suggestions please email: shli@stat.wvu.edu.
References
Bentley J.L. (1975), “Multidimensional binary search trees used for associative
search,” Communication ACM, 18, 309-517.
Arya S. and Mount D.M. (1993),
“Approximate nearest neighbor searching,”
Proc. 4th Ann. ACM-SIAM Symposium on Discrete Algorithms (SODA'93), 271-280.
Arya S., Mount D.M., Netanyahu N.S., Silverman R. and Wu A.Y. (1998),
“An optimal algorithm for approximate nearest neighbor searching,”
Journal of the ACM, 45, 891-923.
Beygelzimer A., Kakade S. and Langford J. (2006),
“Cover trees for nearest neighbor,”
ACM Proc. 23rd international conference on Machine learning, 148, 97-104.