---
name: "mlpack_kernel_NystroemMethod"
section: "3"
platform: "linux"
package: "mlpack-doc"
version: "1.0.10-1"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/mlpack_kernel_NystroemMethod"
---

# mlpack\_kernel\_NystroemMethod(3)

## NAME

mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \> -

## SYNOPSIS

### Public Member Functions

**NystroemMethod** (const arma::mat &**data**, KernelType &**kernel**, const size\_t **rank**)\
 *Create the* **NystroemMethod** *object.*  void **Apply** (arma::mat &output)\
 *Apply the low-rank factorization to obtain an output matrix G such that K' = G \* G^T.*  void **GetKernelMatrix** (const arma::mat \***data**, arma::mat &miniKernel, arma::mat &semiKernel)\
 *Construct the kernel matrix with matrix that contains the selected points.*  void **GetKernelMatrix** (const arma::Col\< size\_t \> &selectedPoints, arma::mat &miniKernel, arma::mat &semiKernel)\
 *Construct the kernel matrix with the selected points.*

### Private Attributes

const arma::mat & **data**\
 *The reference dataset.*  KernelType & **kernel**\
 *The locally stored kernel, if it is necessary.*  const size\_t **rank**\
 *Rank used for matrix approximation.*

## Detailed Description

### template\<typename KernelType, typename PointSelectionPolicy = KMeansSelection\<\>\>class mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \>

Definition at line 38 of file nystroem\_method.hpp.

## Constructor & Destructor Documentation

### template\<typename KernelType, typename PointSelectionPolicy = KMeansSelection\<\>\> mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \>::NystroemMethod (const arma::mat &data, KernelType &kernel, const size\_trank)

Create the **NystroemMethod** object. The constructor here does not really do anything.

**Parameters:**

*data* Data matrix. \
 *kernel* Kernel to be used for computation. \
 *rank* Rank to be used for matrix approximation.

## Member Function Documentation

### template\<typename KernelType, typename PointSelectionPolicy = KMeansSelection\<\>\> void mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \>::Apply (arma::mat &output)

Apply the low-rank factorization to obtain an output matrix G such that K' = G \* G^T.

**Parameters:**

*output* Matrix to store kernel approximation into.

Referenced by mlpack::kpca::NystroemKernelRule\< KernelType, PointSelectionPolicy \>::ApplyKernelMatrix().

### template\<typename KernelType, typename PointSelectionPolicy = KMeansSelection\<\>\> void mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \>::GetKernelMatrix (const arma::mat \*data, arma::mat &miniKernel, arma::mat &semiKernel)

Construct the kernel matrix with matrix that contains the selected points.

**Parameters:**

*data* Data matrix pointer. \
 *miniKernel* to store the constructed mini-kernel matrix in. \
 *miniKernel* to store the constructed semi-kernel matrix in.

### template\<typename KernelType, typename PointSelectionPolicy = KMeansSelection\<\>\> void mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \>::GetKernelMatrix (const arma::Col\< size\_t \> &selectedPoints, arma::mat &miniKernel, arma::mat &semiKernel)

Construct the kernel matrix with the selected points.

**Parameters:**

*points* Indices of selected points. \
 *miniKernel* to store the constructed mini-kernel matrix in. \
 *miniKernel* to store the constructed semi-kernel matrix in.

## Member Data Documentation

### template\<typename KernelType, typename PointSelectionPolicy = KMeansSelection\<\>\> const arma::mat& mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \>::data` [private]`

The reference dataset.

Definition at line 83 of file nystroem\_method.hpp.

### template\<typename KernelType, typename PointSelectionPolicy = KMeansSelection\<\>\> KernelType& mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \>::kernel` [private]`

The locally stored kernel, if it is necessary.

Definition at line 85 of file nystroem\_method.hpp.

### template\<typename KernelType, typename PointSelectionPolicy = KMeansSelection\<\>\> const size\_t mlpack::kernel::NystroemMethod\< KernelType, PointSelectionPolicy \>::rank` [private]`

Rank used for matrix approximation.

Definition at line 87 of file nystroem\_method.hpp.

## Author

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