MATLAB核函数算法

function [K] = kernel(ker,x,y) % Calculate kernel function. % % x: 输入样本,d×n1的矩阵,n1为样本个数,d为样本维数 % y: 输入样本,d×n2的矩阵,n2为样本个数,d为样本维数 % % ker 核参数(结构体变量) % the following fields: % type - linear : k(x,y) = x'*y % poly : k(x,y) = (x'*y+c)^d % gauss : k(x,y) = exp(-0.5*(norm(x-y)/s)^2) % tanh : k(x,y) = tanh(g*x'*y+c) % degree - Degree d of polynomial kernel (positive scalar). % offset - Offset c of polynomial and tanh kernel (scalar, negative for tanh). % width - Width s of Gauss kernel (positive scalar). % gamma - Slope g of the tanh kernel (positive scalar). % % ker = struct('type','linear'); % ker = struct('type','ploy','degree',d,'offset',c); % ker = struct('type','gauss','width',s); % ker = struct('type','tanh','gamma',g,'offset',c); % % K: 输出核参数,n1×n2的矩阵 %-------------------------------------------------------------% switch ker.type case 'linear' K = x'*y; case 'ploy' d = ker.degree; c = ker.offset; K = (x'*y+c).^d; case 'gauss' s = ker.width; rows = size(x,2); cols = size(y,2); tmp = zeros(rows,cols); for i = 1:rows for j = 1:cols tmp(i,j) = norm(x(:,i)-y(:,j)); end end K = exp(-0.5*(tmp/s).^2); case 'tanh' g = ker.gamma; c = ker.offset; K = tanh(g*x'*y+c); otherwise K = 0; end