How to place 2 numbers on a matrix randomly but besides each other

Hi all

I have a 10*10 matrix and i want to place 2 (two's) randomly on that matrix but they must always be besides each other

i need to do this for 3,4,5 where i need to place 3(three's) randomly on the matrix but besides each other and 4(fours) besides each other etc....

how do i do this?

i need to add these numbers on this matrix

BSgrid=zeros(10);

thanks in advance

Answer 1

[Image Analyst]

Use randi() to get a random location inside the matrix, then place the other 2 next to it.

Try this and adapt as needed:

m = zeros(10, 10) % Whatever your original matrix is.
[rows, columns] = size(m)
randomRow = randi([2, rows-1], 1)
randomCol = randi([2, columns-1], 1)
direction = randi(8, 1)
% Assign initial 2
m(randomRow, randomCol) = 2;
% Assign the additional 2 in one of the 8 surrounding pixels.
switch direction
	case 1
		m(randomRow-1, randomCol-1) = 2;
	case 2
		m(randomRow-1, randomCol) = 2;
	case 3
		m(randomRow-1, randomCol+1) = 2;
	case 4
		m(randomRow, randomCol-1) = 2;
	case 5
		m(randomRow, randomCol-1) = 2;
	case 6
		m(randomRow+1, randomCol-1) = 2;
	case 7
		m(randomRow+1, randomCol) = 2;
	case 8
		m(randomRow+1, randomCol+1) = 2;
end
m

[Tarek Eid]

Thanks for the reply.

It is worth noting that I am an absolute beginner on Matlab and thus I'm afraid I don't understand your code so can you please explain it to me?

I know its too much to ask, but if you can explain it, It would mean a lot to me and I would be grateful.

[Image Analyst]

Well first you want to assign a random row don't you. So we need to get a random row and a random column. But because I want to allow for a neighbor that is anywhere around it (in the 8 neighboring elements), I can't go from the first to the last. I can only go from the second to the next to the last (which is indicated by end-1). So I get those and then assign it:

% Assign initial 2
m(randomRow, randomCol) = 2;

Next I need to get a neighbor for that in one of the 8 elements surrounding that random location. And I don't want to always pick the location to the right of it of course. I want to be able to pick ANY of the 8 locations to place the neighbor. So I get a random integer from 1 to 8, indicating which direction, from the one I already placed, the new one should be placed. So I need to assign it somewhere in the range of (randomRow - 1) to (randomRow + 1) for the row, and similar for the column: (randomCol - 1) to (randomCol + 1) for the column. So direction is a random number from 1 to 8 and the switch statement will go into the case that matches the number it is. Then, inside the case, I assign the second "2" to the proper location. Note that each case is in a different location with respect to the one I already placed.

Tarek, if this worked, could you please "Accept this answer"? Thanks in advance.