OpenCV: cv::ml::KNearest Class Reference

| OpenCV 3.4.2 Open Source Computer Vision

Public Types | Public Member Functions | Static Public Member Functions | List of all members
cv::ml::KNearest Class Referenceabstract
Machine Learning

The class implements K-Nearest Neighbors model. More...

`#include "ml.hpp"`

Inheritance diagram for cv::ml::KNearest:

## Public Types
enum | Types { BRUTE_FORCE =1, KDTREE =2 }
| Implementations of KNearest algorithm. More...
Public Types inherited from cv::ml::StatModel
enum | Flags { UPDATE_MODEL = 1, RAW_OUTPUT =1, COMPRESSED_INPUT =2, PREPROCESSED_INPUT =4 }

## Public Member Functions
virtual float | findNearest (InputArray samples, int k, OutputArray results, OutputArray neighborResponses=noArray(), OutputArray dist=noArray()) const =0
| Finds the neighbors and predicts responses for input vectors. More...
virtual int | getAlgorithmType () const =0
virtual int | getDefaultK () const =0
virtual int | getEmax () const =0
virtual bool | getIsClassifier () const =0
virtual void | setAlgorithmType (int val)=0
virtual void | setDefaultK (int val)=0
virtual void | setEmax (int val)=0
virtual void | setIsClassifier (bool val)=0
Public Member Functions inherited from cv::ml::StatModel
virtual float | calcError (const Ptr< TrainData > &data, bool test, OutputArray resp) const
| Computes error on the training or test dataset. More...
virtual bool | empty () const CV_OVERRIDE
| Returns true if the Algorithm is empty (e.g. in the very beginning or after unsuccessful read. More...
virtual int | getVarCount () const =0
| Returns the number of variables in training samples. More...
virtual bool | isClassifier () const =0
| Returns true if the model is classifier. More...
virtual bool | isTrained () const =0
| Returns true if the model is trained. More...
virtual float | predict (InputArray samples, OutputArray results=noArray(), int flags=0) const =0
| Predicts response(s) for the provided sample(s) More...
virtual bool | train (const Ptr< TrainData > &trainData, int flags=0)
| Trains the statistical model. More...
virtual bool | train (InputArray samples, int layout, InputArray responses)
| Trains the statistical model. More...
Public Member Functions inherited from cv::Algorithm
| Algorithm ()
virtual | ~Algorithm ()
virtual void | clear ()
| Clears the algorithm state. More...
virtual String | getDefaultName () const
virtual void | read (const FileNode &fn)
| Reads algorithm parameters from a file storage. More...
virtual void | save (const String &filename) const
virtual void | write (FileStorage &fs) const
| Stores algorithm parameters in a file storage. More...
void | write (const Ptr< FileStorage > &fs, const String &name=String()) const
| simplified API for language bindings This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. More...

## Static Public Member Functions
static Ptr< KNearest > | create ()
| Creates the empty model. More...
Static Public Member Functions inherited from cv::ml::StatModel
template<typename _Tp >
static Ptr< _Tp > | train (const Ptr< TrainData > &data, int flags=0)
| Create and train model with default parameters. More...
Static Public Member Functions inherited from cv::Algorithm
template<typename _Tp >
static Ptr< _Tp > | load (const String &filename, const String &objname=String())
| Loads algorithm from the file. More...
template<typename _Tp >
static Ptr< _Tp > | loadFromString (const String &strModel, const String &objname=String())
| Loads algorithm from a String. More...
template<typename _Tp >
static Ptr< _Tp > | read (const FileNode &fn)
| Reads algorithm from the file node. More...

## Additional Inherited Members
Protected Member Functions inherited from cv::Algorithm
void | writeFormat (FileStorage &fs) const

## Detailed Description

The class implements K-Nearest Neighbors model.

See also
  K-Nearest Neighbors

## Member Enumeration Documentation

## ◆ Types

enum cv::ml::KNearest::Types

Implementations of KNearest algorithm.

Enumerator
BRUTE_FORCE |
KDTREE |

## Member Function Documentation

## ◆ create()

static Ptr<KNearest> cv::ml::KNearest::create | ( |  | ) |
| static

Creates the empty model.

The static method creates empty KNearest classifier. It should be then trained using StatModel::train method.

## ◆ findNearest()

virtual float cv::ml::KNearest::findNearest | ( | InputArray | samples,
|  | int | k,
|  | OutputArray | results,
|  | OutputArray | neighborResponses = `noArray()`,
|  | OutputArray | dist = `noArray()`
| ) |  | const
| pure virtual

Finds the neighbors and predicts responses for input vectors.

Parameters

  samples | Input samples stored by rows. It is a single-precision floating-point matrix of `<number_of_samples> * k` size.
  k | Number of used nearest neighbors. Should be greater than 1.
  results | Vector with results of prediction (regression or classification) for each input sample. It is a single-precision floating-point vector with `<number_of_samples>` elements.
  neighborResponses | Optional output values for corresponding neighbors. It is a single- precision floating-point matrix of `<number_of_samples> * k` size.
  dist | Optional output distances from the input vectors to the corresponding neighbors. It is a single-precision floating-point matrix of `<number_of_samples> * k` size.

For each input vector (a row of the matrix samples), the method finds the k nearest neighbors. In case of regression, the predicted result is a mean value of the particular vector's neighbor responses. In case of classification, the class is determined by voting.

For each input vector, the neighbors are sorted by their distances to the vector.

In case of C++ interface you can use output pointers to empty matrices and the function will allocate memory itself.

If only a single input vector is passed, all output matrices are optional and the predicted value is returned by the method.

The function is parallelized with the TBB library.

## ◆ getAlgorithmType()

virtual int cv::ml::KNearest::getAlgorithmType | ( |  | ) | const
| pure virtual

Algorithm type, one of KNearest::Types.

See also
  setAlgorithmType

## ◆ getDefaultK()

virtual int cv::ml::KNearest::getDefaultK | ( |  | ) | const
| pure virtual

Default number of neighbors to use in predict method.

See also
  setDefaultK

## ◆ getEmax()

virtual int cv::ml::KNearest::getEmax | ( |  | ) | const
| pure virtual

Parameter for KDTree implementation.

See also
  setEmax

## ◆ getIsClassifier()

virtual bool cv::ml::KNearest::getIsClassifier | ( |  | ) | const
| pure virtual

Whether classification or regression model should be trained.

See also
  setIsClassifier

## ◆ setAlgorithmType()

virtual void cv::ml::KNearest::setAlgorithmType | ( | int | val | ) |
| pure virtual

See also
  getAlgorithmType

## ◆ setDefaultK()

virtual void cv::ml::KNearest::setDefaultK | ( | int | val | ) |
| pure virtual

See also
  getDefaultK

## ◆ setEmax()

virtual void cv::ml::KNearest::setEmax | ( | int | val | ) |
| pure virtual

See also
  getEmax

## ◆ setIsClassifier()

virtual void cv::ml::KNearest::setIsClassifier | ( | bool | val | ) |
| pure virtual

See also
  getIsClassifier

The documentation for this class was generated from the following file:

- ml/include/opencv2/ml.hpp