Plotting 3 for loops at once.

I am trying to create a for loop that goes through the loop with values theta 0 through 15. There is a value v_perp defined in the loop, and I want the plot to be of theta on the x axis and v_perp on the y. I am able to get all 3 to plot at the same time but there is one point for each loop that is way off from the other points and I am not sure why. Here is my code so far:

v_min = 16.5;

v_avg = 18;

v_max = 19.5;

x_r = 21.45;

y_r = 1.265;

for theta = 0:15

A = -9.81/2;

B = (v_min*sin(30))+(v_min*cos(30)*tan(theta));

C = 1.265+21.45*(tan(theta));

y = [A B C];

t = roots(y);

t_first = t(1);

v_perp(theta+1) = (-sind(-theta)*(16.5*cosd(30)))+(cosd(-theta)*((-9.81*t_first)+(16.5*cosd(30))));

v_tot = sqrt((16.5*cosd(30)).^2+(((-9.81*t)+(16.5*cosd(30)))).^2);

if v_perp(theta+1) > 0.4*v_tot

point(theta+1) = true;

   else

     point(theta+1) = false;

    end

end

v_perp(~point) = nan;

theta = 0:15;

plot(theta,v_perp,'r.','MarkerSize',15)

hold on

for theta = 0:15

      A = -9.81/2;

      B = (v_max*sin(30))+(v_max*cos(30)*tan(theta));
      C = 1.265+21.45*(tan(theta));
      y = [A B C];
      t = roots(y);
      t_first = t(1);
      v_perp2(theta+1) = (-sind(-theta)*(16.5*cosd(30)))+(cosd(-theta)*((-9.81*t_first)+(16.5*cosd(30))));
      v_tot = sqrt((16.5*cosd(30)).^2+(((-9.81*t)+(16.5*cosd(30)))).^2);
      if v_perp2(theta+1) > 0.4*v_tot
          point(theta+1) = true;
      else
          point(theta+1) = false;
      end
  end
  v_perp2(~point) = nan;
  theta = 0:15;
  plot(theta,v_perp2,'b.','MarkerSize',15)
  hold on

for theta = 0:15

      A = -9.81/2;
      B = (v_avg*sin(30))+(v_avg*cos(30)*tan(theta));
      C = 1.265+21.45*(tan(theta));
      y = [A B C];
      t = roots(y);
      t_first = t(1);
      v_perp3(theta+1) = (-sind(-theta)*(16.5*cosd(30)))+(cosd(-theta)*((-9.81*t_first)+(16.5*cosd(30))));
      v_tot = sqrt((16.5*cosd(30)).^2+(((-9.81*t)+(16.5*cosd(30)))).^2);
      if v_perp3(theta+1) > 0.4*v_tot
          point(theta+1) = true;
      else
          point(theta+1) = false;
      end
  end
  v_perp3(~point) = nan;
  theta = 0:15;
  plot(theta,v_perp3,'k.','MarkerSize',15)

disp(theta)
disp(t)
disp(v_perp)
disp(v_tot)