CODEWITHSUNDEEP
matlab
user38375
user38375

Reputation: 31

draw circle around data in a grid (MATLAB)

I have 100 data points scattered within a region. Now I divided the region with 6x6 equisized grids and now it looks like according the figure below:

figure http://s2.postimg.org/c6zk68myf/IGN2.png

Now I need to to draw a circle within a box of a grid so that I could group points in a box if there is more than 1 point. If this is the case, there shall be no circle within a box if there are none or one points in a box.

Any idea on what I should do?

Here is my MATLAB code for the plot I created above:

xm=100;
ym=100;

%x and y Coordinates of the Sink
sink.x=0.5*xm;
sink.y=0.5*ym;

%Number of Nodes in the field
n=100

figure(1);
for i=1:1:n
    S(i).xd=rand(1,1)*xm;
    XR(i)=S(i).xd;
    S(i).yd=rand(1,1)*ym;
    YR(i)=S(i).yd;
    S(i).G=0;
    %initially there are no cluster heads only nodes
    S(i).type='N';

        plot(S(i).xd,S(i).yd,'o');
        hold on;

   
end
NrGrid = 6;   
                               % Number Of Grids
x = linspace(0, 100, NrGrid+1);
[X,Y] = meshgrid(x);
S(n+1).xd=sink.x;
S(n+1).yd=sink.y;
plot(S(n+1).xd,S(n+1).yd,'x',X,Y,'k');
 hold on
plot(Y,X,'k')
    set(gca, 'Box','off', 'XTick',[], 'YTick',[])
axis square
        
%First Iteration
figure(1);

Expected result:

http://i.share.pho.to/27ae061b_o.jpeg

Upvotes: 3

Views: 1087

Answers (1)

Ander Biguri
Ander Biguri

Reputation: 35525

So the proccess you need to go to get there is the following:

  1. Get in which grid the points are
  2. Compute the minimum radius circle (I used this FEX submission, you can do it yourself or check how it is performed in the PDF that comes with it)
  3. Plot the circles

So here there is a piece of code that does 1-2

%% Where are the points?
% I am not going to modify your `S` variable, but you could do this inside
% it
points=[S(1:end-1).xd; S(1:end-1).yd];
gridind=zeros(size(points,2),1);
Grid=NrGrid^2;
for ii=1:NrGrid
    for jj=1:NrGrid
        % get points in the current square
        ind=points(1,:)>X(1,ii)& points(1,:)<X(1,ii+1)...
             & points(2,:)>Y(jj,1)& points(2,:)<Y(jj+1,1);
        % save index
        gridind(ind)=(ii-1)*NrGrid+(jj-1)+1;
    end
end

% now that we know in wich grid each point is lets find out wich ones are
% not
c=zeros(NrGrid^2,2);
r=zeros(NrGrid^2,1);

for ii=1:NrGrid^2
    if sum(gridind==ii)>1
        [c(ii,:), r(ii)] = minboundcircle(points(1,gridind==ii),points(2,gridind==ii));

    else
        c(ii,:)=nan;
        r(ii)=nan;
    end
end

and here a piece of code that plots them

theta=linspace(0,2*pi,20);

offs=1; % For beauty purposes
for ii=1:NrGrid^2
    if ~isnan(c(ii))
        xc=(r(ii)+offs).*cos(theta)+c(ii,1);
        yc=(r(ii)+offs).*sin(theta)+c(ii,2);
        plot(xc,yc,'r');
    end
end

axis([min(X(:)) max(X(:)) min(Y(:)) max(Y(:)) ])

Result:

enter image description here

You could easily draw ellipses changing a bit the code, using for example this FEX submission.

Ask if you don't understand something, but should be straightforward.

Upvotes: 4

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