scipy.spatial.cKDTree.query¶
- cKDTree.query(self, x, k=1, eps=0, p=2, distance_upper_bound=np.inf, workers=1)¶
Query the kd-tree for nearest neighbors
- Parameters
- xarray_like, last dimension self.m
An array of points to query.
- klist of integer or integer
The list of k-th nearest neighbors to return. If k is an integer it is treated as a list of [1, … k] (range(1, k+1)). Note that the counting starts from 1.
- epsnon-negative float
Return approximate nearest neighbors; the k-th returned value is guaranteed to be no further than (1+eps) times the distance to the real k-th nearest neighbor.
- pfloat, 1<=p<=infinity
Which Minkowski p-norm to use. 1 is the sum-of-absolute-values “Manhattan” distance 2 is the usual Euclidean distance infinity is the maximum-coordinate-difference distance A finite large p may cause a ValueError if overflow can occur.
- distance_upper_boundnonnegative float
Return only neighbors within this distance. This is used to prune tree searches, so if you are doing a series of nearest-neighbor queries, it may help to supply the distance to the nearest neighbor of the most recent point.
- workersint, optional
Number of workers to use for parallel processing. If -1 is given all CPU threads are used. Default: 1.
Changed in version 1.6.0: The “n_jobs” argument was renamed “workers”. The old name “n_jobs” is deprecated and will stop working in SciPy 1.8.0.
- Returns
- darray of floats
The distances to the nearest neighbors. If
x
has shapetuple+(self.m,)
, thend
has shapetuple+(k,)
. When k == 1, the last dimension of the output is squeezed. Missing neighbors are indicated with infinite distances.- indarray of ints
The index of each neighbor in
self.data
. Ifx
has shapetuple+(self.m,)
, theni
has shapetuple+(k,)
. When k == 1, the last dimension of the output is squeezed. Missing neighbors are indicated withself.n
.
Notes
If the KD-Tree is periodic, the position
x
is wrapped into the box.When the input k is a list, a query for arange(max(k)) is performed, but only columns that store the requested values of k are preserved. This is implemented in a manner that reduces memory usage.
Examples
>>> import numpy as np >>> from scipy.spatial import cKDTree >>> x, y = np.mgrid[0:5, 2:8] >>> tree = cKDTree(np.c_[x.ravel(), y.ravel()])
To query the nearest neighbours and return squeezed result, use
>>> dd, ii = tree.query([[0, 0], [2.2, 2.9]], k=1) >>> print(dd, ii, sep='\n') [2. 0.2236068] [ 0 13]
To query the nearest neighbours and return unsqueezed result, use
>>> dd, ii = tree.query([[0, 0], [2.2, 2.9]], k=[1]) >>> print(dd, ii, sep='\n') [[2. ] [0.2236068]] [[ 0] [13]]
To query the second nearest neighbours and return unsqueezed result, use
>>> dd, ii = tree.query([[0, 0], [2.2, 2.9]], k=[2]) >>> print(dd, ii, sep='\n') [[2.23606798] [0.80622577]] [[ 6] [19]]
To query the first and second nearest neighbours, use
>>> dd, ii = tree.query([[0, 0], [2.2, 2.9]], k=2) >>> print(dd, ii, sep='\n') [[2. 2.23606798] [0.2236068 0.80622577]] [[ 0 6] [13 19]]
or, be more specific
>>> dd, ii = tree.query([[0, 0], [2.2, 2.9]], k=[1, 2]) >>> print(dd, ii, sep='\n') [[2. 2.23606798] [0.2236068 0.80622577]] [[ 0 6] [13 19]]