How to reduce dimensions of 31 ECG beat signals which are in matrix form?

clear all;

close all;

clc;

addpath(genpath('E:\project af\hosa'));

load 'E:\data\AF.mat';

mat1=[];

x=segment(1,:);

plot(x);

n=20;

for k=-n:n,

cmat(:,k+n+1)=cumest(x,3,n,200,0,'biased',k);

end

mat1=[mat1;cmat];

mesh(-n:n,-n:n, cmat)

clear all;

close all;

clc;

load 'E:\data1\matlab3.mat';

cmat_new=[];

for i=1:21

cmat_new=[cmat_new mat1(i,1:21)];

m=mean(cmat_new);

end