How can I randomly pick a row (A) from a matrix give the same value from array (B)?

I have a coordinate matrix (A) which is nx2, and an index array (B) which is nx1. for example:

A=[1,2; 0,3; 3,8; 6,5; ....; 3,7];

B=[1;2;2;3;1;1;3;...3; 2];

I want to randomly pick a row from A which has the same value group from B. for example:

G1=random a row [Ax1, Ay1; such that B=1];

G2=random a row [Ax2, Ay2; such that B=2];

G3=random a row [Ax3, Ay3; such that B=3]; and so on

G1,G2 ... are 1x2 corrdinate arrays.

Is there a command or simple algorithm to do the reandom assigmenet

[Zhi Yuan Liao]

Thank you Guillaume. It works!

Answer 1

[Guillaume]

If I understood correctly:

[~, ~, uid] = unique(B);  %If B is an array of integers from 1 with no gaps, then uid will be the same as B and this line is not needed
result = splitapply(@(rows) A(rows(randi(numel(rows))), :), (1:size(A, 1))', uid)

result(1, :) will be a random row of A for which the uid of the B values is 1

result(2, :) will be a random row of A for which the uid of the B values is 2

etc...