how to access 31 signals

clear all;

close all;

clc;

m1=[];

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

for j=1:31

y=mat1(j,:);

cmat_new=[];

for i=1:21

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

end

m=mean(cmat_new);

m1=[m1;m];

end