function [data] = Kernel(x,xi,sig)
    m = size(x,1);
    data = zeros(m,1);
    for i = 1 : m
% 线性核
%         data(i) = x(i,:) * xi';
% 高斯核
        deltaRow = x(i,:) - xi;
        data(i) = exp( - deltaRow * deltaRow' / (sig ^ 2));
% 拉普拉斯核
%         deltaRow = x(i,:) - xi;
%         data(i) = exp( - sqrt(deltaRow * deltaRow') / sig);
    end
end