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How to create a checkerboard matrix without inbuilt function.

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Riley Smith
Riley Smith on 12 Sep 2017
Commented: Mendi on 6 Sep 2020
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

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Cedric Wannaz
Cedric Wannaz on 12 Sep 2017
You can also use
abs(sin(...)) or abs(cos(...))
with the proper arguments.
Cedric Wannaz
Cedric Wannaz on 28 Nov 2017
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

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Accepted Answer

Joseph Cheng
Joseph Cheng on 12 Sep 2017
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

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More Answers (4)

ksam K
ksam K on 25 Nov 2017
%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

Jan Siegmund
Jan Siegmund on 21 May 2020
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]);

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Mendi
Mendi on 5 Sep 2020
It is more natural to use modulus on meshgrid:
[iX,iY] = meshgrid(1:8,1:8);
Mask=mod(iX+iY,2);

Bruno Luong
Bruno Luong on 5 Sep 2020
Edited: Bruno Luong on 5 Sep 2020
Two more methods
toeplitz(mod(0:7,2))
or for even size
kron(ones(4),[0 1;1 0])

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