getfvb(A,M,N,mode)

GETFVB Get the first values of blocks of a matrix.
B = GETFVB(A,M,N) for a matrix A returns a matrix containing first values
of blocks with size [M N] of a matrix given A.

B = GETFVB(A,M,N,'vect') for a matrix A returns an arry containing first values
of blocks with size [M N] of a matrix given A.
If someone want to improuve or adding some changes, only let me know
about that

Examples:
A=[ 1 2 3 4
5 6 7 8
9 1 1 2
2 4 5 6 ]

B = getfvb(A,2,2)
% returns
B=[ 1 3
9 1 ]
B = getfvb(A,2,2,'vect')
% returns
B=[ 1 9 3 1]


A=[ 1 2 3 4
5 6 7 8
9 1 1 2
2 4 5 6 ]

B = getfvb(A,1,2)
% returns
B=[ 1 3
5 7
9 1
2 5 ]
B = getfvb(A,1,2,'vect')
% returns
B=[ 1 5 9 2 3 7 1 5]