How to respresent and plot data while on loop in Matlab?

What I'm trying to to is to simulate the position of two satellites and to determine if they will collide. For that I'm using a Rk4 method. As you can see, in the loop I have the drawnow command that adds a point on a 3d graph, after avery iteration. What I'm interested in is to find a way to represent the 3d plot until the condition of collision meets (where I have the message) and also to get the values on the .txt file, while in the loop not outside. When I use the return command, and try to plot or to add text, I have an error "vectors must be the same length" and doesn't let me obtain the data. That happens because lets say sat1=1X200 while tspan=1X201. Is there any other command that I could use instead of return or a better solution?

Here is my code:

    figure(1);
  orbitsat1=animatedline('Color','r');

orbitsat2=animatedline('Color','g');

msat1=124;
msat2=234;
Asat1=2.2;
Asat2=3.2;

sat10(1,1)=   453322.3616  ;
sat10(2,1)=   -2346021.219 ;
sat10(3,1)=     -7894131.349 ;
sat10(4,1)=     2142.38067;
sat10(5,1)=   7487.44895   ;
sat10(6,1)=     -9864.00872;

sat20(1,1)=   543322.3616  ;
sat20(2,1)=   -3246021.219 ;
sat20(3,1)=     -8794131.349 ;
sat20(4,1)=     1242.38067;
sat20(5,1)=   4787.44895   ;
sat20(6,1)=     -8964.00872;

tspan = 0:200;
secpday = 60*60*24;
a1 = 2018;
la1 = 1;
z1 = 2;
o1 = 12;
m1 = 0;
s1 = 0;
n1 = datenum(a1,la1,z1,o1,m1,s1);

n1 = n1 + tspan/secpday;

[an,luna,zi,ora,min,sec] = datevec(n1);

h=1;
sat1 = zeros(6, tspan(end)/h);
sat1(:,1) = sat10;

sat2 = zeros(6, tspan(end)/h);
sat2(:,1) = sat20;

for i=1:(tspan(end)/h)
    k_1 = simsat1(tspan(i), sat1(:,i), msat1, Asat1, sat1(4:6, i));
    k_2 = simsat1(tspan(i)+0.5*h, sat1(:,i)+0.5*h*k_1,msat1, Asat1, sat1(4:6, i));
    k_3 = simsat1((tspan(i)+0.5*h), (sat1(:,i)+0.5*h*k_2),  msat1, Asat1, sat1(4:6, i));        k_4 = simsat1((tspan(i)+h),(sat1(:,i)+k_3*h), msat1, Asat1, sat1(4:6, i));

      k_12 = simsat2(tspan(i), sat2(:,i),  msat2, Asat2, sat2(4:6, i));
      k_22 = simsat2(tspan(i)+0.5*h, sat2(:,i)+0.5*h*k_12,  msat2, Asat2, sat2(4:6, i));
      k_32 = simsat2((tspan(i)+0.5*h), (sat2(:,i)+0.5*h*k_22), msat2, Asat2, sat2(4:6, i));
      k_42 = simsat2((tspan(i)+h),(sat2(:,i)+k_32*h),  msat2, Asat2, sat2(4:6, i));

      sat2(:,i+1) = double(sat2(:,i) + (1/6)*(k_12+2*k_22+2*k_32+k_42)*h);
      sat1(:,i+1) = double(sat1(:,i) + (1/6)*(k_1+2*k_2+2*k_3+k_4)*h);
      addpoints(orbitsat1,sat1(1,i),sat1(2,i),sat1(3,i));
      drawnow update
      hold off

      Rorb = ((sat1(1,i).^2 + sat1(2,i).^2 + sat1(3,i).^2).^0.5);
      Rcsc = ((sat2(1,i).^2 + sat2(2,i).^2 + sat2(3,i).^2).^0.5);
      dif=Rorb-Rcsc;

      if (dif >0.5*10^10 && dif < 2*10^5) && i>350
          Message = sprintf('Data:\nan:%d\nluna:%d\nzi:%d\nora:%d\nminut:%d\nsecunda:%d',an(i),luna(i),zi(i),ora(i),min(i),sec(i));
          msgbox(Message)
          msgbox('Coliziune!','Coliziune','warn',Message);
          return
      end
  end

Pozx=sat1(1,:);
Pozy=sat1(2,:);
Pozz=sat1(3,:);

Tbody=[an; luna; zi ;ora; min; sec; Pozx; Pozy; Pozz];
twobody = fopen('nobody.txt','w');
fprintf(twobody,'Rezultate Twobody (metri) \n\n');
fprintf(twobody,'  An  luna  zi   ora min sec            pozitia pe  x     pozitia pe  y      pozitia pe  z       viteza pe  x    viteza pe  y    viteza pe  z\n\n');
fprintf(twobody,'---------------------------------------------------------------------------------------------------------------------------------------------\n%6d-%3d-%3d\t%3d:%3d:%3d\t\t\t\t%12.6f\t%12.6f\t\t%12.6f\t\t%12.6f\t%\n',Tbody);
fclose(twobody);
where simsat1

function sat1prim=simsat1(t,sat1,msat1,Asat1,vit)
miu=398600.4418*10^9;
magn=(sat1(1)^2+sat1(2)^2+sat1(3)^2)^(3/2);
sat1prim=zeros(6,1);
sat1prim(1,1)=sat1(4);
sat1prim(2,1)=sat1(5);
sat1prim(3,1)=sat1(6);
sat1prim(4,1)=double(-miu*sat1(1)/magn);
sat1prim(5,1)=double(-miu*sat1(2)/magn);
sat1prim(6,1)=double(-miu*sat1(3)/magn);
end
and simsat2

function sat2prim=simsat2(t,sat2,msat2,Asat2,vit)
miu=398600.4418*10^9;
magn=(sat2(1)^2+sat2(2)^2+sat2(3)^2)^(3/2);
sat2prim=zeros(6,1);
sat2prim(1,1)=sat2(4);
sat2prim(2,1)=sat2(5);
sat2prim(3,1)=sat2(6);
sat2prim(4,1)=double(-miu*sat2(1)/magn);
sat2prim(5,1)=double(-miu*sat2(2)/magn);
sat2prim(6,1)=double(-miu*sat2(3)/magn);
end

[James Tursa]

I don't understand your collision criteria. In the first place, you are comparing the radius values:

      Rorb = ((sat1(1,i).^2 + sat1(2,i).^2 + sat1(3,i).^2).^0.5);
      Rcsc = ((sat2(1,i).^2 + sat2(2,i).^2 + sat2(3,i).^2).^0.5);
      dif=Rorb-Rcsc;

You could have a very small dif value but the satellites could be on opposite sides of the Earth. I would have expected something like this instead:

      dif = norm(sat1(1:3,i) - sat2(1:3,i));

And, secondly, how can the following condition ever be satisfied? How can diff be larger than 0.5*10^10 and at the same time be smaller than 2*10^5? This can't happen since the first number is larger than the second number.

      if (dif >0.5*10^10 && dif < 2*10^5) && i>350

[Alexandru Lapusneanu]

HI James! I know that those are wrong, but I'm using them just to test the collision detector. Those conditions are absurd and will be changed. You could put instead of

if (dif >0.5*10^10 && dif < 2*10^5) && i>350

something like

if i>350

[James Tursa]

OK, we'll set that aside for now. What does the code for addpoints look like? What is it supposed to do? Why can't you just replot the corrent set of points instead of "adding" points to the current plot?

[Alexandru Lapusneanu]

addpoints is a matlab syntax. First you have to declare an animated line, as I did with orbitsat1, and after that you put addpoints inside a for loop and as the loop iterates , that command will add a point to the orbisat1 ,describing the orbit of the satellite. I want to have a visual representation of the orbit after every step, not after I iterated all the values. In this way, if there is a collision I could stop the iteration. That is the main point.

[James Tursa]

So, is this all supposed to be inside a function, and you want to return the satellite positions up to the point of the collision to the caller? But you are having some type of problem doing that?

[Alexandru Lapusneanu]

Indeed , thats the problem. When there is a collision I would want to stop the loop, to display the "collision message" and all the positions over iterated time should be saved in the .txt file.