How to check a row in a matrix against every other row in a different matrix.

I am trying to use circcirc to check for intersections of a circle against every other circle that has been generated as I plot them on a graph. I am struggling to think of a way to make this happen. What I have so far is a for loop but it just confuses me the more I think about it, and help would be greatly appreciated

%For circle 
if shape == 1
    
    %Number of Shapes
    shapeAmount =10000 
    
    %shape size(for now goes from 1 to shapeSize)
    shapeSize = 1000
    shapeSizeArray = rand(shapeAmount, 1) * shapeSize;
    
    %ask for placements of shapes (Arbritary for now)
    shapePlaceX = rand(shapeAmount,1)*100000;
    shapePlaceY = rand(shapeAmount,1)*100000;
    hold on;
 
    %Generate first circle to check against
    th = 0:pi/50:2*pi;
    xunit = shapeSizeArray(1) * cos(th) + shapePlaceX(1);
    yunit = shapeSizeArray(1) * sin(th) + shapePlaceY(1);
    plot(xunit,yunit)
    
    %Make array of center point and radius to check against other circles
    circlestats = [shapePlaceX(1), shapePlaceY(1), shapeSizeArray(1)];
    
    %Check if circles intersect
    %if they do, throw away, if they don't keep and plot
    count = 1
     
    while count <= shapeAmount
           
           for N = 1:size(circlestats,1)
                [xCheck,yCheck] = circcirc(shapePlaceX(N+1), shapePlaceY(N+1), shapeSizeArray(N+1), circlestats(count,1), circlestats(count,2), circlestats(count,3));
            
                
                    
               
                if count >= shapeAmount
                    continue
                
                elseif sum(isnan(xCheck)) ~= 0
                    circlestats = [circlestats; shapePlaceX(count), shapePlaceY(count), shapeSizeArray(count)];
                    xunit = shapeSizeArray(count) * cos(th) + shapePlaceX(count);
                    yunit = shapeSizeArray(count) * sin(th) + shapePlaceY(count);
                    plot(xunit,yunit)
                    N = N+1;
                    count = count+1
                    
                 else 
                     circlestats = [circlestats; shapePlaceX(1), shapePlaceY(1), shapeSizeArray(1)];
            
                    
                end
           end
    end
   
  hold off
   

[Ameer Hamza]

Can you describe what the format of data you have is? How many matrices you have and what type of data they hold. How do you want to compare them row by row?

[Stefan Lewoski]

I only have one matrix, but it could be two. The matrix has 3 columns, and an ever increasing amount of rows until the amount of rows hit 1000(This number is meant to represent the number of circles on the graph, but I've been struggling).

The matrix has the xposition, yposition, and radius of a circle. The other matrix is just a compilation of all circles that don't intersect. I want to add each circle that passes to the other matrix.

What I would like to happen is use the position and radius of the test circle, and test it against every other circle that has passed the test. It doesn't necceserily have to be a loop, that's just the only way I could think of to do it. Does that make sense?

[Deepak Gupta]

Hello Stefen,

Problem is not very clear. Looking at code, its hard to understand what you are trying to achive. I see following possibilities.

1. You have one circle and want to find out if this circle touches other circles from a set of circles.
2. You have a set of circles and want to find out if circles from this set touch the circles from other sets
3. You have only one set of circles and want to find out which circles touch each other and plot them only if they touch atleast one other circle.

Please clarify further. You are also trying to create another circlestats matrix in the program, whats the point of it?

Thanks,

Deepak

[Stefan Lewoski]

Hi, I have posted the whole code, hopefully that clears things up a little.

It is almost number 1. I have a set of circles A(the number of circles in the set grows). I also have a set of circles B which I would like to check if it intersects with any circles in set A. If it doesn't intersect, it is added to the set A. This process was meant to repeat until all of B has been checked against all of A, at which point all the circles in A are plotted on a graph.

Answer 1

[Deepak Gupta]

Hello Stefen,

Here is a piece of code. There is a list of non overlapping circles and a list of circles to be tested against non overlapping list. If we find a new circle not over lapping with existing non overlapping list of circles then we add this circles to the list of non over lapping circles and then test new circle for no overlap against this latest non- overlapping list of circles. If i understood you correctly, then this i what you want.

shapePlaceX = 20*rand(10, 1);
shapePlaceY = 20*rand(10, 1);
shapeSizeArray = 5*rand(10, 1);

circlestats = [shapePlaceX, shapePlaceY, shapeSizeArray]; %Circles to be compared with test circle.
nointersectCircles = [0, 0, 1]; %Initial test circle
noinstersectCount = 1;
flag =0;

for count= 1:size(shapePlaceX, 1)
    for ii = 1:noinstersectCount
        [xCheck,yCheck] = circcirc(nointersectCircles(ii, 1), nointersectCircles(ii, 2), nointersectCircles(ii, 3), circlestats(count,1), circlestats(count,2), circlestats(count,3));
        if ~isnan(xCheck)
            flag =1; 
            break;
        end
    end
    if(flag ==0)
        nointersectCircles = [nointersectCircles; circlestats(count, :)];  %Circle which passes test of no touch, will be added to no intersect list.
        noinstersectCount = noinstersectCount+1; % Increase the no intersect count accordingly.
    end
    flag = 0;
end
subplot(3, 1, 1)
viscircles( [nointersectCircles(1,1), nointersectCircles(1,2)], nointersectCircles(1,3));
subplot(3, 1, 2)
viscircles( [circlestats(:, 1), circlestats(:, 2)], circlestats(:, 3));
subplot(3, 1, 3)
viscircles( [nointersectCircles(:, 1), nointersectCircles(:, 2)], nointersectCircles(:, 3));

Hope this helps.

Thanks,

Deepak

[Stefan Lewoski]

Thanks a lot, I will test this code as well!

[Deepak Gupta]

Hello Stefen,

As circcirc returns nan if two circles have same property(same x, y coordinates and radius) and i am not putting any extra checks in there is repition of circles so circles with same properties will also be added to the non-overlapping list.

[Stefan Lewoski]

Hi, this is exactly what I was looking for, Thankyou!

Answer 2

[Ameer Hamza]

Try the code without any loop. It stores all the non-overlapping circles in 'no_overlap_cir'.

x = [12*rand(5,2)-6 6*rand(5,1)]; % random circles

centers = x(:,1:2);
radius = x(:,3);
center_dist = pdist2(centers, centers);
radius_sum = radius + radius.';

idx = find(sum(center_dist > radius_sum) == (numel(radius)-1));
no_overlap_cir = x(idx, :);

Following code helps in visualizing that the logic is correct. Run this complete code, and it will show the circles on axes. You can see that non-overlapping circles are placed in no_overlap_cir

x = [12*rand(5,2)-6 6*rand(5,1)]; % random circles
 
figure;
ax = axes();
axis([-10 10 -10 10]);
axis equal
for i=1:size(x)
    images.roi.Circle(ax, 'Center', x(i,1:2), 'Radius', x(i,3), 'Label', num2str(i));
end

centers = x(:,1:2);
radius = x(:,3);
center_dist = pdist2(centers, centers);
radius_sum = radius + radius.';

idx = find(sum(center_dist > radius_sum) == (numel(radius)-1));
no_overlap_cir = x(idx, :);

[Stefan Lewoski]

I got the error Unable to resolve the name images.roi.Circle, but I'm guessing that part is just making a circle so I will try it manually to see if that does it. Thank you!

Edit: Nevermind, I figured out I needed the image processing tool box. I will test out the code again now.

[Ameer Hamza]

Yes, that part is just for visualization. It is part of the Image processing toolbox and was introduced in R2018b. So it might not be available in your MATLA installation. You can write the code yourself or take 4, 5 circles with known center and radius to check the results.

[Stefan Lewoski]

Hi, so I took a bit trying to understand what was going on with the code. I am struggling to put into words why it isn't doing quiet what I wanted it to, despite it being really close, but I will try anyway

I think what I want to happen is for overlaps to only be checked against what is in no_overlap_cir. Is that possible?

Thank you for your time.

[Ameer Hamza]

Ok. It is a bit clear now. My current code only has circles that overlap with no other circles. But your requirement seems different.

Can you explain what happens in the beginning when the matrix no_overlap_cir is empty? Fill it with the first circle?

[Stefan Lewoski]

Sorry, I don't think I understand what you are asking me.

When I leave the code as is, but with, say, 500 random circles, no_overlap_cir is empty

I'm not sure what you mean by fill it with the first cirlce. Do you mean start it off with a circle already in the no_overlap_cir index?

[Ameer Hamza]

Ok. I read your question again. Is this correct:

Say you have 500 random circles. You take the first circle and put it in the matrix no_overlap_cir. Then you take the second circle and check if it overlaps with the circle in the no_overlap_cir. If yes, then it is discarded, and if no, then it is added to the matrix no_overlap_cir. And the process continues till the last circle.

If this is correct?

[Stefan Lewoski]

Yes that is correct. I will mention just in case that it should be checked against every circle that is in no_overlap_cir not just one.