   function [A] = blur1d(m)
%% function [A] = blur1d(m)  
%% defines a simple 1-dimensional blurring matrix
%%
 A=(3*diag(ones(m,1),0)+2*diag(ones(m-1,1),1) ... 
  + 2*diag(ones(m-1,1),-1)+diag(ones(m-2,1),2) ...
  + diag(ones(m-2,1),-2));
 A = A'*A;
 A = A / norm(A);   %% normalize to make A not too large
%%
