Question

What matlab command, or combination of commands (using 25 characters or less), could be used to create the following matrix?

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

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

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

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

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

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

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

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Hint: Look for a lower triangluar matrix that is repeated many times. First try to produce that lower triangular matrix with as few characters as possible.

Answer 1

% idea is to generate a lower triangular matrix of size 4x4 and repeat it

A = ones(4) %generate a matrix of ones of size 4 x 4

A = tril(A) % convert it inot a lower triangular matrix of size 4 x 4

B = repmat(A, 2, 5) % repeat the matrix in 2 rows and 5 columns

OUTPUT

ans =

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

Answer 2

We make a lower triangular matrix using the following command :-

We now try to make the desired matrix by concatenating A fives times along the row and two times along the column. We do this using the following command :