scipy.spatial.cKDTree¶

class
scipy.spatial.
cKDTree
¶ kdtree for quick nearestneighbor lookup
This class provides an index into a set of kdimensional points which can be used to rapidly look up the nearest neighbors of any point.
The algorithm used is described in Maneewongvatana and Mount 1999. The general idea is that the kdtree is a binary trie, each of whose nodes represents an axisaligned hyperrectangle. Each node specifies an axis and splits the set of points based on whether their coordinate along that axis is greater than or less than a particular value.
During construction, the axis and splitting point are chosen by the “sliding midpoint” rule, which ensures that the cells do not all become long and thin.
The tree can be queried for the r closest neighbors of any given point (optionally returning only those within some maximum distance of the point). It can also be queried, with a substantial gain in efficiency, for the r approximate closest neighbors.
For large dimensions (20 is already large) do not expect this to run significantly faster than brute force. Highdimensional nearestneighbor queries are a substantial open problem in computer science.
Parameters: data : array_like, shape (n,m)
The n data points of dimension m to be indexed. This array is not copied unless this is necessary to produce a contiguous array of doubles, and so modifying this data will result in bogus results. The data are also copied if the kdtree is built with copy_data=True.
leafsize : positive int, optional
The number of points at which the algorithm switches over to bruteforce. Default: 16.
compact_nodes : bool, optional
If True, the kdtree is built to shrink the hyperrectangles to the actual data range. This usually gives a more compact tree that is robust against degenerated input data and gives faster queries at the expense of longer build time. Default: True.
copy_data : bool, optional
If True the data is always copied to protect the kdtree against data corruption. Default: False.
balanced_tree : bool, optional
If True, the median is used to split the hyperrectangles instead of the midpoint. This usually gives a more compact tree and faster queries at the expense of longer build time. Default: True.
boxsize : array_like or scalar, optional
Apply a md toroidal topology to the KDTree.. The topology is generated by \(x_i + n_i L_i\) where \(n_i\) are integers and \(L_i\) is the boxsize along ith dimension. The input data shall be wrapped into \([0, L_i)\). A ValueError is raised if any of the data is outside of this bound.
Attributes
data (ndarray, shape (n,m)) The n data points of dimension m to be indexed. This array is not copied unless this is necessary to produce a contiguous array of doubles. The data are also copied if the kdtree is built with copy_data=True. leafsize (positive int) The number of points at which the algorithm switches over to bruteforce. m (int) The dimension of a single datapoint. n (int) The number of data points. maxes (ndarray, shape (m,)) The maximum value in each dimension of the n data points. mins (ndarray, shape (m,)) The minimum value in each dimension of the n data points. tree (object, class cKDTreeNode) This class exposes a Python view of the root node in the cKDTree object. size (int) The number of nodes in the tree. Methods
count_neighbors
(self, other, r[, p, ...])Count how many nearby pairs can be formed. query
(self, x[, k, eps, p, ...])Query the kdtree for nearest neighbors query_ball_point
(self, x, r[, p, eps])Find all points within distance r of point(s) x. query_ball_tree
(self, other, r[, p, eps])Find all pairs of points whose distance is at most r query_pairs
(self, r[, p, eps])Find all pairs of points whose distance is at most r. sparse_distance_matrix
(self, other, max_distance)Compute a sparse distance matrix