??? Error using ==> mtimes MTIMES is not fully supported for integer classes. At least one input must be scalar. Error in ==> lpre at 16 v(:,:,k)=(​inv(X'*X))​*X'*y;%err​ror coefficients

hello

I have taken 256*256 image. i need to find linear prediction for the image using four neighbours.Then i need to calculate error values.while doing this prediction, i get error in the particular line.

clc;
clear all;
close all;
a=imread('E:/celulas.jpg');

[m n]=size(a);
B = padarray(a,[1 1]);
[m1 n1]=size(B);
A=B;
%linear prediction
k=1;
for i=2:(m1-1)
    for j=2:(n1-1)
        A(i,j)=(B(i-1,j)/4)+(B(i+1,j)/4)+(B(i,j-1)/4)+(B(i,j+1)/4);%replacing center value with 4 neighbours
        X=[B(i-1,j);B(i+1,j);B(i,j-1);B(i,j+1)];%context vectors
        y=B(i,j);
        *v(:,:,k)=(inv(X'*X))*X'*y;%errror coefficients*-getting error in this line
        xhat=v(:,:,k)*X;%predicted pixel
        yhat(i-1,j-1)=xhat;%predicted image
        e(i-1,j-1)=abs(B(i-1,j-1)-xhat);
        k=k+1;
        B(i,j)=A(i,j);%updating the value

      end
  end

but when i convert image into double ,i dont get error why?-without changing the format i want to get the values.kindly provide me suggestions thanks in advance

[poonguzhali p]

sir, i need 1X4 1024 v vectors,v is prediction coefficient.why am insisting in int class is,i need to further embed bits into the original image based on error value.my actual work is watermarking .when i embed the bits into image(using double class),the watermarked image is blank(fully white).

Answer 1

[Matt J]

You should convert to double as you have done. There's no clear reason to prefer integer format for what you are doing and the operations you are doing are not defined for integers in any case. I would, however, recommend that you re-implement the calculation of v(:,:,k) as follows

    v(:,:,k)=X\y;   %instead of (inv(X'*X))*X'*y;

[poonguzhali p]

sir, i need 1X4 1024 v vectors,v is prediction coefficient.why am insisting in int class is,i need to further embed bits into the original image based on error value.my actual work is watermarking .when i embed the bits into image(using double class),the watermarked image is blank(fully white).