Improving my code - I'm trying to generate a checkerboard of size (222,786); length of each size 20. My code did work but I feel the logic can be improved. Kindly help.

% Channel number 90 to 875

chan = 1:1:786;

no_of_chan=length(chan);

% ffid 77 to 298

ffid = 1:1:222;

no_of_ffid=length(ffid);

% Pre-declaring 'checker' - it is two dimensional

checker=zeros(no_of_ffid,no_of_chan);

% Parameter to switch between positive and negative trains within if
% statement

anomaly=-1;

% 1 cell = 100 metres

dimension=20; 

% train is the size of one edge of one checker

train=ones(1,dimension);

for i=1:ceil((no_of_chan/dimension) - 1 )

      if anomaly==1

          train = [train ones(1,dimension)];

             anomaly=-1;

     else

         train = [train -1*ones(1,dimension)];

             anomaly=1;

     end 

end

for i=1:no_of_ffid

      if anomaly==1

          checker(i,:)=train(1:no_of_chan);

          if rem(i,dimension)==0

              anomaly=-1;

          end

      else 

          checker(i,:)=-1*train(1:no_of_chan);

          if rem(i,dimension)==0

              anomaly=1;

          end

      end

end

imshow(checker);

[Image Analyst]

Why not simply use the built-in checkerboard() function, in the Image Processing Toolbox?

[Bhargav Boddupalli]

I tried it but I couldn't generate with required dimensions - 222x786

Answer 1

[John D'Errico]

Shiver. Yes, it can be improved. :) Honestly, what you have done is highly convoluted. That is not bad for someone learning to program. But you are thinking in terms of loops. You are growing arrays dynamically. There are branches and tests in your code when none need exist.

You want to create an array, of size 222x786. Alternating black and white squares, of size 20? The white squares will be 1, the black squares filled with -1?

rdim = 222;
cdim = 786;
squaresize = 20;

[rind,cind] = ndgrid(0:rdim-1,0:cdim-1);
rind = floor(rind/squaresize);
cind = floor(cind/squaresize);

checker = 1 - 2*mod(rind + cind,2);

You want to start thinking in terms of arrays, and what you can do with them, how to work with them.

[Bhargav Boddupalli]

Great! Thanks.