---
name: "mlpack_kernel"
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"
---

# mlpack\_kernel(3)

Kernel functions.

## NAME

mlpack::kernel -

Kernel functions.

## SYNOPSIS

### Classes

class **CosineDistance**\
 *The cosine distance (or cosine similarity).*  class **EpanechnikovKernel**\
 *The Epanechnikov kernel, defined as.*  class **ExampleKernel**\
 *An example kernel function.*  class **GaussianKernel**\
 *The standard Gaussian kernel.*  class **HyperbolicTangentKernel**\
 *Hyperbolic tangent kernel.*  class **KernelTraits**\
 *This is a template class that can provide information about various kernels.*  class **KernelTraits\< CosineDistance \>**\
 *Kernel traits for the cosine distance.*  class **KernelTraits\< EpanechnikovKernel \>**\
 *Kernel traits for the Epanechnikov kernel.*  class **KernelTraits\< GaussianKernel \>**\
 *Kernel traits for the Gaussian kernel.*  class **KernelTraits\< LaplacianKernel \>**\
 *Kernel traits of the Laplacian kernel.*  class **KernelTraits\< SphericalKernel \>**\
 *Kernel traits for the spherical kernel.*  class **KernelTraits\< TriangularKernel \>**\
 *Kernel traits for the triangular kernel.*  class **KMeansSelection**\
 class **LaplacianKernel**\
 *The standard Laplacian kernel.*  class **LinearKernel**\
 *The simple linear kernel (dot product).*  class **NystroemMethod**\
 class **OrderedSelection**\
 class **PolynomialKernel**\
 *The simple polynomial kernel.*  class **PSpectrumStringKernel**\
 *The p-spectrum string kernel.*  class **RandomSelection**\
 class **SphericalKernel**\
 class **TriangularKernel**\
 *The trivially simple triangular kernel, defined by.*

## Detailed Description

Kernel functions.

This namespace contains kernel functions, which evaluate some kernel function $ K(x, y) $ for some arbitrary vectors $ x $ and $ y $ of the same dimension. The single restriction on the function $ K(x, y) $ is that it must satisfy Mercer's condition:

.PP for all square integrable functions $ g(x) $.

The kernels in this namespace all implement the same methods as the **ExampleKernel** class. Any additional custom kernels should implement all the methods that class implements; in addition, any method using a kernel should rely on any arbitrary kernel function class having a default constructor and a function

```
double Evaluate(arma::vec&, arma::vec&);
```

## Author

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