MATLAB最大均值差异(Maximum Mean Discrepancy)

源域：
2.1789	1.7811	5.079	4.9312
0.8621	2.1287	4.9825	2.3388
2.6347	1.9563	4.5392	4.8442
2.7179	2.9001	4.9027	4.8582
2.6686	1.6799	4.3792	4.6411
1.6736	2.3081	4.8384	3.2979
1.5666	2.6467	5.0504	4.459
-0.5611	2.2365	4.3925	5.1316
5.6693	1.7355	4.5335	4.6407
3.2032	2.103	4.1948	5.2605
3.3525	2.8301	4.6383	5.6972
-1.0407	3.5198	4.7106	4.9243
3.9229	2.1161	4.5666	1.772
2.5607	3.802	4.2681	4.6322
3.3072	2.5083	4.6095	2.2236
2.7121	2.4338	4.136	2.2348
5.3547	2.1088	4.402	4.9884
1.8302	1.4921	4.6216	3.5862
2.8891	2.1286	4.6419	3.8606
-0.0896	2.6894	3.6843	6.6392
3.1404	1.9461	4.2604	5.9859
2.3406	3.1988	5.0872	4.7518
2.5067	2.9704	4.2749	4.3441
8.2153	1.7592	5.2409	3.8201
0.3027	2.7589	3.9826	4.8484
4.0223	1.7566	4.6219	4.92
6.1367	2.1098	4.7832	5.4567
4.9795	2.418	4.7726	3.1959
-1.0746	2.4311	4.7683	4.5599
5.4939	2.6046	4.4663	5.1159
4.5709	1.9838	4.9596	4.9317
1.3746	2.6845	5.1921	3.2068
1.7178	0.7976	4.6948	3.7012
目标域：
1.9584	2.0242	4.7594	2.587
-2.8342	3.4594	4.4371	5.2375
1.6251	2.7737	5.0145	6.3262
0.7016	2.5265	4.8881	3.2105
3.5579	2.5773	4.856	4.283
4.3282	2.7581	4.7095	6.715
3.1619	2.5427	4.1323	5.5883
4.9933	2.2985	3.8455	3.8381
3.2214	2.6478	4.3276	2.5246
-0.2848	2.5853	4.6481	3.4857
2.876	1.5096	3.9921	2.4505
0.8559	2.5633	5.483	3.0589
4.2149	2.6618	4.2017	3.3713

function mmd_XY=my_mmd(X, Y, sigma)
%Author：kailugaji
%Maximum Mean Discrepancy 最大均值差异 越小说明X与Y越相似
%X与Y数据维度必须一致, X, Y为无标签数据，源域数据，目标域数据
%mmd_XY=my_mmd(X, Y, 4)
%sigma is kernel size, 高斯核的sigma
[N_X, ~]=size(X);
[N_Y, ~]=size(Y);
K = rbf_dot(X,X,sigma); %N_X*N_X
L = rbf_dot(Y,Y,sigma);  %N_Y*N_Y
KL = rbf_dot(X,Y,sigma);  %N_X*N_Y
c_K=1/(N_X^2);
c_L=1/(N_Y^2);
c_KL=2/(N_X*N_Y);
mmd_XY=sum(sum(c_K.*K))+sum(sum(c_L.*L))-sum(sum(c_KL.*KL));
mmd_XY=sqrt(mmd_XY);

function H=rbf_dot(X,Y,deg)
%Author：kailugaji
%高斯核函数/径向基函数 K(x, y)=exp(-d^2/sigma), d=(x-y)^2, 假设X与Y维度一样
%Deg is kernel size,高斯核的sigma
[N_X,~]=size(X);
[N_Y,~]=size(Y);
G = sum((X.*X),2);
H = sum((Y.*Y),2);
Q = repmat(G,1,N_Y(1));
R = repmat(H',N_X(1),1);
H = Q + R - 2*X*Y';
H=exp(-H/2/deg^2);  %N_X*N_Y

>> mmd_XY=my_mmd(x, y, 4)
 
mmd_XY =
 
    0.1230