KNeighborsClassifier
¶
-
class
ibex.sklearn.neighbors.
KNeighborsClassifier
(n_neighbors=5, weights='uniform', algorithm='auto', leaf_size=30, p=2, metric='minkowski', metric_params=None, n_jobs=1, **kwargs)¶ Bases:
sklearn.neighbors.classification.KNeighborsClassifier
,ibex._base.FrameMixin
Note
The documentation following is of the class wrapped by this class. There are some changes, in particular:
- A parameter
X
denotes apandas.DataFrame
. - A parameter
y
denotes apandas.Series
.
Classifier implementing the k-nearest neighbors vote.
Read more in the User Guide.
- n_neighbors : int, optional (default = 5)
- Number of neighbors to use by default for
kneighbors()
queries. - weights : str or callable, optional (default = ‘uniform’)
weight function used in prediction. Possible values:
- ‘uniform’ : uniform weights. All points in each neighborhood are weighted equally.
- ‘distance’ : weight points by the inverse of their distance. in this case, closer neighbors of a query point will have a greater influence than neighbors which are further away.
- [callable] : a user-defined function which accepts an array of distances, and returns an array of the same shape containing the weights.
- algorithm : {‘auto’, ‘ball_tree’, ‘kd_tree’, ‘brute’}, optional
Algorithm used to compute the nearest neighbors:
- ‘ball_tree’ will use
BallTree
- ‘kd_tree’ will use
KDTree
- ‘brute’ will use a brute-force search.
- ‘auto’ will attempt to decide the most appropriate algorithm
based on the values passed to
fit()
method.
Note: fitting on sparse input will override the setting of this parameter, using brute force.
- ‘ball_tree’ will use
- leaf_size : int, optional (default = 30)
- Leaf size passed to BallTree or KDTree. This can affect the speed of the construction and query, as well as the memory required to store the tree. The optimal value depends on the nature of the problem.
- p : integer, optional (default = 2)
- Power parameter for the Minkowski metric. When p = 1, this is equivalent to using manhattan_distance (l1), and euclidean_distance (l2) for p = 2. For arbitrary p, minkowski_distance (l_p) is used.
- metric : string or callable, default ‘minkowski’
- the distance metric to use for the tree. The default metric is minkowski, and with p=2 is equivalent to the standard Euclidean metric. See the documentation of the DistanceMetric class for a list of available metrics.
- metric_params : dict, optional (default = None)
- Additional keyword arguments for the metric function.
- n_jobs : int, optional (default = 1)
- The number of parallel jobs to run for neighbors search.
If
-1
, then the number of jobs is set to the number of CPU cores. Doesn’t affectfit()
method.
>>> X = [[0], [1], [2], [3]] >>> y = [0, 0, 1, 1] >>> from sklearn.neighbors import KNeighborsClassifier >>> neigh = KNeighborsClassifier(n_neighbors=3) >>> neigh.fit(X, y) KNeighborsClassifier(...) >>> print(neigh.predict([[1.1]])) [0] >>> print(neigh.predict_proba([[0.9]])) [[ 0.66666667 0.33333333]]
RadiusNeighborsClassifier KNeighborsRegressor RadiusNeighborsRegressor NearestNeighbors
See Nearest Neighbors in the online documentation for a discussion of the choice of
algorithm
andleaf_size
.Warning
Regarding the Nearest Neighbors algorithms, if it is found that two neighbors, neighbor k+1 and k, have identical distances but different labels, the results will depend on the ordering of the training data.
-
fit
(X, y)¶ Note
The documentation following is of the class wrapped by this class. There are some changes, in particular:
- A parameter
X
denotes apandas.DataFrame
. - A parameter
y
denotes apandas.Series
.
Fit the model using X as training data and y as target values
- X : {array-like, sparse matrix, BallTree, KDTree}
- Training data. If array or matrix, shape [n_samples, n_features], or [n_samples, n_samples] if metric=’precomputed’.
- y : {array-like, sparse matrix}
- Target values of shape = [n_samples] or [n_samples, n_outputs]
- A parameter
-
kneighbors
(X=None, n_neighbors=None, return_distance=True)¶ Note
The documentation following is of the class wrapped by this class. There are some changes, in particular:
- A parameter
X
denotes apandas.DataFrame
. - A parameter
y
denotes apandas.Series
.
Finds the K-neighbors of a point.
Returns indices of and distances to the neighbors of each point.
- X : array-like, shape (n_query, n_features), or (n_query, n_indexed) if metric == ‘precomputed’
- The query point or points. If not provided, neighbors of each indexed point are returned. In this case, the query point is not considered its own neighbor.
- n_neighbors : int
- Number of neighbors to get (default is the value passed to the constructor).
- return_distance : boolean, optional. Defaults to True.
- If False, distances will not be returned
- dist : array
- Array representing the lengths to points, only present if return_distance=True
- ind : array
- Indices of the nearest points in the population matrix.
In the following example, we construct a NeighborsClassifier class from an array representing our data set and ask who’s the closest point to [1,1,1]
>>> samples = [[0., 0., 0.], [0., .5, 0.], [1., 1., .5]] >>> from sklearn.neighbors import NearestNeighbors >>> neigh = NearestNeighbors(n_neighbors=1) >>> neigh.fit(samples) NearestNeighbors(algorithm='auto', leaf_size=30, ...) >>> print(neigh.kneighbors([[1., 1., 1.]])) (array([[ 0.5]]), array([[2]]...))
As you can see, it returns [[0.5]], and [[2]], which means that the element is at distance 0.5 and is the third element of samples (indexes start at 0). You can also query for multiple points:
>>> X = [[0., 1., 0.], [1., 0., 1.]] >>> neigh.kneighbors(X, return_distance=False) array([[1], [2]]...)
- A parameter
-
predict
(X)[source]¶ Note
The documentation following is of the class wrapped by this class. There are some changes, in particular:
- A parameter
X
denotes apandas.DataFrame
. - A parameter
y
denotes apandas.Series
.
Predict the class labels for the provided data
- X : array-like, shape (n_query, n_features), or (n_query, n_indexed) if metric == ‘precomputed’
- Test samples.
- y : array of shape [n_samples] or [n_samples, n_outputs]
- Class labels for each data sample.
- A parameter
-
predict_proba
(X)[source]¶ Note
The documentation following is of the class wrapped by this class. There are some changes, in particular:
- A parameter
X
denotes apandas.DataFrame
. - A parameter
y
denotes apandas.Series
.
Return probability estimates for the test data X.
- X : array-like, shape (n_query, n_features), or (n_query, n_indexed) if metric == ‘precomputed’
- Test samples.
- p : array of shape = [n_samples, n_classes], or a list of n_outputs
- of such arrays if n_outputs > 1. The class probabilities of the input samples. Classes are ordered by lexicographic order.
- A parameter
-
score
(X, y, sample_weight=None)¶ Note
The documentation following is of the class wrapped by this class. There are some changes, in particular:
- A parameter
X
denotes apandas.DataFrame
. - A parameter
y
denotes apandas.Series
.
Returns the mean accuracy on the given test data and labels.
In multi-label classification, this is the subset accuracy which is a harsh metric since you require for each sample that each label set be correctly predicted.
- X : array-like, shape = (n_samples, n_features)
- Test samples.
- y : array-like, shape = (n_samples) or (n_samples, n_outputs)
- True labels for X.
- sample_weight : array-like, shape = [n_samples], optional
- Sample weights.
- score : float
- Mean accuracy of self.predict(X) wrt. y.
- A parameter
- A parameter