# Filling missing points in a grid

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fatoma Saml on 2 May 2021
Edited: fatoma Saml on 16 Aug 2021
Hi everyone
I am wondering if anyone can help to mark the missing points on the grid with (x) . I have a regular points in x,y that I get from executing the differences between a predeifined points to get the grid, at the same time, some points are missing and I want to mark them (x red) as shown in the figure (i.e, (7,8), and the other missing points. How to select specific range of points with their index as marked in the black sqaure .
I have execute the code
M=3; N=4;
mN=[0:M-1]*N;
nM=[0:N-1]*M;
[xx yy]=meshgrid(mN, mN);
[x y]=meshgrid(nM, nM);
L1=[xx(:),yy(:)];
L2=[x(:),y(:)];
LL=[0,0];
L1= union(L1, L2, 'rows');
S=union(L1,LL,'rows');
figure
plot(S(:, 1),S(:,2) ,'o','color', 'b', 'markersize',4, 'linewidt',1);
LEN_S = size(S, 1);
MAX_x = max(S(:, 1));
MIN_x = min(S(:, 1));
MAX_y = max(S(:, 2));
MIN_y = min(S(:, 2));
[mx_mat, my_mat] = ndgrid(-(MAX_x - MIN_x):(MAX_x - MIN_x), -(MAX_y - MIN_y):(MAX_y - MIN_y));
mx_vec = mx_mat(:); my_vec = my_mat(:);
w = zeros(size(mx_vec));
n1 = cell(size(mx_vec));
n2 = cell(size(mx_vec));
for ii = 1 : size(S, 1)
for jj = 1 : size(S, 1)
index = (mx_vec == S(ii, 1) - S(jj, 1) & my_vec == S(ii, 2) - S(jj, 2));
w( index ) = w( index ) + 1;
n1{ index } = [n1{ index }; S(ii, :)];
n2{ index } = [n2{ index }; S(jj, :)];
end
end
D = [mx_vec, my_vec];
LEN_S = size(S, 1);
SS = repmat(S, [LEN_S, 1]);
SS_= kron(S, ones(LEN_S, 1));
[D1, ~, ind_SS] = unique(SS - SS_, 'rows', 'sorted');
fh2= figure (2);
plot(D1(:,1), D1(:,2) ,'square','color', 'r', 'markersize',5, 'linewidt',2);hold on
plot(D1(:,1), D1(:,2) ,'square','color', 'b', 'markersize',5, 'linewidt',2);hold on
axis([-inf inf -inf inf ]);
I apperciate any help
Thanks

Doddy Kastanya on 5 May 2021
You could try to add the following at the end of your code:
hold on
text(7,8,'X','color','r')
If there are other points, then you could embed this in a for loop identifying the appropriate x and y position.

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