Randomly convert exact number of 1 to 0 in binary matrix

Hi.

I have binary matrix 3x3.

0 1 0
1 0 1
1 1 1

Let say, it includes six "1" values on random positions. I need to convert two "1" to "0", but randomly.

0 1 0
1 0 0
1 0 1

one of the possible outcomes.

Thank you for your help!

Answer 1

[per isakson]

Try

%%
x = [ 0 1 0
      1 0 1
      1 1 1];
%%
ix_one = find( x == 1 );
ix_set_zero = randi( numel(ix_one), 1,2 );
x( ix_one( ix_set_zero ) ) = 0

[mnemonix]

Thank you very much for your useful and rapid answer. I really appreciate your help.

[per isakson]

Thanks for accepting, however, there is a flaw in my answer. randi() may return two equal numbers, which leads to that only one 1 is replaced by 0.

>> randi( 6, 1,2 )
ans =
     6     6
>> 
>> m = 1:8;
>> m([6,6])=0
m =
     1     2     3     4     5     0     7     8
>> 

With or without replacement, the statement

ix_set_zero = randi( numel(ix_one), 1,2 );

needs to be replaced by

ix_set_zero = randperm( numel(ix_one), 2 );

[mnemonix]

Thanks for warning.

Answer 2

[Stephen23]

>> M = [0,1,0;1,0,1;1,1,1]
M =
     0     1     0
     1     0     1
     1     1     1
>> X = find(M);
>> M(X(randperm(numel(X),2))) = 0
M =
     0     0     0
     1     0     1
     1     1     0