function plot_demo_func                          %       J. M. Hill    ss13
%Demonstration of plot function and subscripted variables      
%g=gravity, m/s/s; m=mass,kg; Cd= second-order drag coef, kg/m
g=9.81; m=68.1; cd=.25;
for i = 1:21  %vectorize time and velocity for use in the plot function
    t(i)=i-1;
    v(i)=vel(g,m,cd,t(i));
end
  plot(t,v) 
  title('Plot of velocity vs. time')
  xlabel('time')
  ylabel('velocity')
  grid
%----------------------------------------------------------------------
function velocity = vel(g,m,cd,time)
velocity = sqrt(g*m/cd)*tanh(sqrt(g*cd/m)*time);