how to compounding more that one matrixs into other matrix?

Question

How to let more than one matrix to compose as one matrix

For example c = {{a, b}, {a, b}}; a = {{1, 0}, {0, 1}}; b = {{1, 1}, {1, 1}};

Answer 1

You can use ArrayFlatten:

c = ArrayFlatten[{{a, b}, {a, b}}]

{{1, 0, 1, 1}, {0, 1, 1, 1}, {1, 0, 1, 1}, {0, 1, 1, 1}}

TeXForm @ MatrixForm @ c

$\left( \begin{array}{cccc} 1 & 0 & 1 & 1 \\ 0 & 1 & 1 & 1 \\ 1 & 0 & 1 & 1 \\ 0 & 1 & 1 & 1 \\ \end{array} \right)$