choose random places on matrix

i need to create a game of maze on matlab. i have zero matrix mXm and i need to insert to the matrix n places which will mark as obsticals, how can i choose n random places on matrix and replace the zeros to 1? (randomly)

Answer 1

[arushi]

Hi Omer,

• randperm: This function generates a random permutation of integers from 1 to totalElements, ensuring that the selected indices for obstacles are unique.

Here is an example :

function maze = createMaze(m, n)
    % Check if the number of obstacles is less than or equal to total matrix elements
    if n > m * m
        error('Number of obstacles cannot exceed the total number of matrix elements.');
    end
    
    % Initialize the m x m matrix with zeros
    maze = zeros(m, m);
    
    % Generate n unique random indices for obstacles
    totalElements = m * m;
    randomIndices = randperm(totalElements, n);
    
    % Convert linear indices to row and column subscripts
    [rowIndices, colIndices] = ind2sub([m, m], randomIndices);
    
    % Place obstacles in the matrix
    for i = 1:n
        maze(rowIndices(i), colIndices(i)) = 1;
    end
end

Hope this helps.

Answer 2

[Image Analyst]

Simply use randperm and linear indexing. No need to figure out or convert locations to (row, column) indexes (that's a waste of time).

m = 7; % Width and height of maze
maze = false(m, m); % Initialize maze to all zeros.  Use logical type to save memory space.
numOnes = round(0.3 * m * m); % 30% of locations will be 1's.
randomLocations = randperm(m * m, numOnes); % Get all locations in a random order.
maze(randomLocations) = 1  % Assign a 1 to those locations.

maze = 7x7 logical array
   0   0   1   0   0   0   0
   0   0   1   0   1   0   0
   1   1   0   0   0   0   0
   0   0   0   1   0   1   0
   0   0   1   0   0   1   0
   0   1   1   0   0   1   0
   0   1   1   1   0   0   0