How to create a checkerboard matrix without inbuilt function.

I just want to write this matrix, but want to do it using for loops

   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0
   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0
   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0
   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0
   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0
   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0
   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0
   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   1   0   1   0   1   0   1   0   1   0   1   0   1   0   1   0

[Riley Smith]

im trying to do it using zero(16) and plussing 1's in certain coordinates, or i could use meshgrid too mesh them together, not sure how i want to do it.

[Stephen23]

@Riley Smith: so try both of them. What is stopping you from trying things out? MATLAB does not explode if your first attempt does not work.

[Adam]

This is one of those problems where there is a vast number of different ways to try it. Many that give the right answer and many that give the wrong answer, but command line testing is free. My first attempt yielded the wrong answer as I forgot that the value at the end of a column is equal to that at the start of the next column. But a little tweak soon fixes those problems and experimenting is fun and good for learning.

[James Tursa]

If you get stuck, or just want to see how others have done this:

https://www.mathworks.com/matlabcentral/newsreader/view_thread/340389#933443

[Rik]

Also, the criterion restricting the use of builtins makes it harde to answer this. It is very difficult to define what counts as a builtin and what doesn't, as that quickly devolves into not being able to use Matlab at all (+ is a builtin as well).

[Cedric]

You can also use

 abs(sin(...))    or    abs(cos(...))

with the proper arguments.

[James Tursa]

Using the sin function for this would be a sin ...

[Cedric]

I had missed this comment ... ;-)

It's one of the rare cases where using a cos would be a sin too ..

0.5-(-1).^((1:n)+(1:n).')/2

or

a = 1 : n ;
a + a.' == 1

Answer 1

[Joseph Cheng]

There are much easier ways to do this than nested for loops, reshape is readily available. if you must do it with for loops you want to start off with the template

 for Rind=1:Nrows
   for Cind=1:Ncols
        Checkerboard(Rind,Cind) = ___;%what condition of Rind and Cind gives you the checker board pattern.
        %start with the first row what makes a 1 appear when Rind==1 and Cind=a number.
        %then think of the sigificant difference between Rind==1 and Rind==2.....
   end
  end

Answer 2

[ksam K]

%Hope this helps you. 
function a = checkerboard(n)
a = zeros(n);
for i = 1:n
    for j = 1:n
        if (i == j)
            a (i, j) = 0;
        elseif (mod(j, 2) == 0) && (mod(i,2) == 0)
             a(i,j) = 0;
        elseif (mod(j, 2) == 0) || (mod(i,2) == 0)
            a(i,j) = 1;
        end
    end
end
end

[Nitika Gupta]

thanks

Answer 3

[Jan Siegmund]

For an even sized checkerboard:

rows = 6;
cols = 4;
normal = repmat(eye(2,'logical'),[rows/2 cols/2]);
% or
inverted = repmat(~eye(2,'logical'),[rows/2 cols/2]);

Answer 4

[Mendi]

It is more natural to use modulus on meshgrid:

[iX,iY] = meshgrid(1:8,1:8);
Mask=mod(iX+iY,2);

[Bruno Luong]

One liner variant

mod((1:8)+(1:8)',2)

[Mendi]

Yeap. The one liner is better.

Answer 5

[Bruno Luong]

Two more methods

toeplitz(mod(0:7,2))

or for even size

kron(ones(4),[0 1;1 0])