Translating MATLAB code into C

Hello guys, I was just wondering if anyone can help translate my code into C as I don't have MATLAB Coder . I am more familiar with MATLAB's array indexing and I believe that C's array indexing is a little too complicated for a beginner like me. I'd appreciate it if you could walk me through the steps..

I am currently stuck at these two lines and I believe C won't allow me to do array indexing the same way MATLAB does:-

b = a(x:x+1, y:y+1);
a(x:x+1, y:y+1) = b;

Here is my entire code :-

a = [1 2 3 4; 2 3 4 5; 3 4 5 6; 4 5 6 7];
c = dctmtx(2);
q_mtx = [16 11; 12 12];

for x = 1:2:M
    for y = 1:2:N

          b = a(x:x+1, y:y+1); %<----HOW DO I DO THIS IN C???

          b = c*b*c';

          b = b./q_mtx ;

          a(x:x+1, y:y+1) = b; 
      end
  end

Answer 1

[Walter Roberson]

     for (xoff = 0, xoff <= 1, xoff++)
       for (yoff = 0, yoff <= 1, yoff++)
         b[yoff][xoff] = a[y+yoff][x+xoff];

That is, you use a loop. Unless you want to start into memcpy().

Notice that I reversed the order of the indices. C arrays are row-major instead of column-major.

Answer 2

[Hiroshi Nakamura]

Thank you so much Walter! I really appreciate it! One more question. What are y and x again in you loop? Also if I were to do it using memcopy, how would I go about doing it? Thanks again!

for (xoff = 0, xoff <= 1, xoff++)
       for (yoff = 0, yoff <= 1, yoff++)
         b[yoff][xoff] = a[y+yoff][x+xoff];