MATLAB: How to make x circles move within a space

Question

I've been able to make a circle move inside a rectangle with this code:

        if (r(2)+R >=b)
            r(2)=b-R;
            v(2)=-v(2)
        end
        plot(r(1)+R*x,r(2)+R*y,'-b','MarkerSize',28*R)
        rectangle('Position',[0,0,a,b])
        axis equal
        pause(dt/deltat)
    
end

how do I do the same thing, but with n circles?

Answer 1

Use logical indexing. For example,

        mask = r(2,:)+R >=b;
        r(2,mask) = b-R;
        v(2,,mask) = -v(2,mask);