MATLAB: Extract a sub-matrix if the first or second column contains a specific number

Question

I have a large matrix A, I want to extract submatrices B1, B2.. etc that contains the same number of columns as in A but only rows for which the first or second columns of A contains a specific number. For instance for this A matrix;

A=[1  4  0  0.0576  0  250  250  250;
4  5  0.017  0.092  0.158  250  250  250;
5  6  0.039  0.17  0.358  150  150  150;
3  6  0  0.0586  0  300  300  300;
6  7  0.0119  0.1008  0.209  150  150  150;
7  8  0.0085  0.072  0.149  250  250  250;
8  2  0  0.0625  0  250  250  250;
8  9  0.032  0.161  0.306  250  250  250;
9  4  0.01  0.085  0.176  250  250  250
]

Extract B such that it contains rows for which column 1 and column 2 in A contain the number '4' B4 should look like this

B4=[1  4  0  0.0576  0  250  250  250;
4  5  0.017  0.092  0.158  250  250  250;
9  4  0.01  0.085  0.176  250  250  250;
]

I have very huge matrices, I am wondering if there is a super efficient way to do this.

Answer 1

ii = 4;
Bii = A(any(A == ii,2),:);