i try to fing energy compaction ratio...please chk my code because i am little bit confuse about the formula of obtaining ECR

 image2=rgb2gray(imread('C:\Users\hp\Desktop\data\1 (4).JPG'));

 wavemngr('del','josh');
 wavemngr('add','shivjoshi','josh',1,'','newwavelet.m');
 OUT1 = wavemngr('read');
 [C,S] = wavedec2(image2,6,'josh');
 thr=1.0000;
 [Xcomp,CXC,LXC,PERF0,PERFL2] =wdencmp('gbl',C,S,'josh',6,thr,'h',1);
% colormap(map);
% subplot(1,2,1); image(K); title('Original Image');
% axis square
% subplot(1,2,2); image(Xcomp); title('Compressed Image');
% axis square
disp('The compression ratio is')
disp(PERF0)
disp('Retained Energy is')
disp(PERFL2)
K=image2;
Z=double(K);
W=double(Xcomp);
M=size(K,1);
N=size(K,2);
for y=1:N
 for x=1:M
    MSE=(1/(M*N))*((Z(x,y))-(W(x,y)))^2;
 end
end
disp('PSNR value of decompressed image is');
 PSNR=10*log10((255^2)/MSE);
 disp(PSNR)

 %ENERGY COMPACTION RATION
 a=0;
 variance=(var(Xcomp,0,1));
 for i=1:size(variance,2)
a=a+variance(1,i);
 end
ecr=a/length(variance)