Add coordinate points to a grid

Hi, I need help. Im trying to create a grid (map of a ground) 200m x 300m and then I need to add some points in the grid. I have the coordinates of the points, but I dont know how to do it. I did the grid with the command [X,Y]= meshgrid() but it created a grid with lines, not an empty grid. So, I need an empty grid in which I can add the points. Thanks so much, Vanessa

[Walter Roberson]

Are you wanting to use the mapping toolbox?

[Vanessa]

I think is not necessary, just a grid in which I could add points (trees) and then evaluate how many of these points are around (e.g. radius of 5 meters) to a specific point.

Answer 1

[Image Analyst]

Why can't you just do

% Create empty grid.  No lines at all, or any points at all.
myGrid = zeros(rows, columns);
% You say you have existing coordinates already.
% Let's assume they are in arrays called x and y
% and have values that correspond to rows and columns.
% Place them in the grid with a value of 1
for k = 1 : length(x)
  myGrid(y(k), x(k)) = 1;
end

[Image Analyst]

To find out which are within a distance of 5 from some other point (x0, y0):

distances = sqrt((x-x0).^2 + (y-y0).^2);
% Get a logical index array of those elements within 5
within5 = distances < 5;
% Now "evaluate how many of these points are around
% (e.g. radius of 5 meters) to a specific point."
howMany = sum(within5);

I think this should get you what you asked for.

[Vanessa]

Thanks so much :)