B = repmat(A,m,n)
B = repmat(A,[m n])
将A矩阵看作元素，复制组成m行n列，即将A复制m*n个
>> A = [1,2;3,4]
A =
1 2
3 4
>> B = repmat(A,2,3)
B =
1 2 1 2 1 2
3 4 3 4 3 4
1 2 1 2 1 2
3 4 3 4 3 4