MATLAB: How can i write F=(1/N).*f​.*double(a​).*f; correctly, the ,matlab(2015a) keeps giving me errors

element-wiseequationMATLABmatrix dimensions must agreetimes

I am trying to do the simulation for the walsh code, here is the code….
%Walsh Transform.
  clear;
  % Reading the image file into variable 'a'.
  a=imread('len.jpg');
  %x=rgb2gray(a);
  N=length(a);
  %Walsh Transform computation
  n=log2(N);
  n=1+fix(n);
  f=ones(N,N);
    for x=1:N; 
        for u=1:N
            p=dec2bin(x-1,n); 
            q=dec2bin(u-1,n);
            for i=1:n; 
                f(x,u)=f(x,u)*((-1)^(p(n+1-i)*q(i)));
            end;
        end;
    end
    *F=(1/N).*f.*double(a).*f;-----i keep having an error at this level*
    % Shifting the Fourier spectrum to the center of the frequency square.
    for i=1:N/2;   
        for j=1:N/2
            G(i+N/2,j+N/2)=F(i,j);
        end;
    end
    for i=N/2+1:N;  
        for j=1:N/2
            G(i-N/2,j+N/2)=F(i,j);
        end;
    end
    for i=1:N/2;    
        for j=N/2+1:N
            G(i+N/2,j-N/2)=F(i,j);
        end;
    end
    for i=N/2+1:N; 
        for j=N/2+1:N
            G(i-N/2,j-N/2)=F(i,j);
        end;
    end
    % Computing and scaling the logarithmic Walsh spectrum.
    H=log(1+abs(G));
    for i=1:N
        H(i,:)=H(i,:)*255/abs(max(H(i,:)));
    end
    % Changing the color map to gray scale (8 bits).
    colormap(gray(255));
    % Showing the main image and its Walsh spectrum.
    subplot(2,2,1),image(a),title('Main image');
    subplot(2,2,2),image(abs(G)),title('Walsh spectrum');
    subplot(2,2,3),image(H),title('Logarithmic scaled Walsh spectrum');
      if true
      if true
        % code

      end
        % code
      end

Best Answer

You are trying to multiply two arrays which have totally different sizes:
>> a = rand(23,99,3);
>> N = length(a);
>> f = ones(N,N);
>> F = (1/N).*f.*double(a).*f
Error using  .* 
Matrix dimensions must agree.
In fact the basic problem is this multiplication:
>> f.*a
Error using  .* 
Matrix dimensions must agree.
So lets have a look at the sizes of those arrays:
>> size(f)
ans =
    99    99
>> size(a)
ans =
    23    99     3
The times documentation clearly states that " Inputs A and B must be the same size unless one is a scalar". Are your two arrays the same size ? What do expect MATLAB to do ?
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