while ((A(i,1)-A(j,1))^2+(A(i,2)-A(j,2))^2+(A(i,3)-A(j,3))^2)<(r(i)+r(j))^2
      A(i,1:3)=r(i)+(200-2*r(i))* rand(1,3);
end
在每次判断的时候 想使j=1：i-1
该怎么处理啊