svkernel.m

来自「支持向量机的核心程序」· M 代码 · 共 44 行

function k = svkernel(ker,u,v,d)
%SVKERNEL kernel for Support Vector Methods
%
%  Usage: k = svkernel(ker,u,v)
%
%  Parameters: ker - kernel type
%              u,v - kernel arguments
%
%  Values for ker: 'linear'  -
%                  'poly'    - p1 is degree of polynomial
%                  'rbf'     - p1 is width of rbfs (sigma)
%                  'sigmoid' - p1 is scale, p2 is offset
%                  'spline'  -
%                  'bspline' - p1 is degree of bspline
%                  'fourier' - p1 is degree
%                  'erfb'    - p1 is width of rbfs (sigma)
%              
%  Author: Steve Gunn ([e-mail])

  if (nargin < 1) % check correct number of arguments
     help svkernel
  else
     
 

    % could check for correct number of args in here
    % but will slow things down further
    switch lower(ker)
      case 'linear'
        k = u*v';
      case 'poly'
        k = (u*v'+1)^2;
      case 'rbf'
        k = exp(-(u-v)*(u-v)'/d);
      
      case 'sigmoid'
        k = tanh(p1*u*v'/length(u) + p2);
      
      otherwise
        k = u*v';
    end

  end