Do you want an image? You can use false
rows = 50; % Whatever you want.
columns = 80;
occupancyMap = false(rows, columns); % Initialize map to no locations being occupied.
then when a certain location needs to marked as "occupied" set that location to true.
occupancyMap(row, col) = true;
If you want certain locations to be "off limits" then you can set them to nan, or set them to true to mean they're already occupied and not available to be occupied by any robot wishing to move there.
