' fpltlib.bas - jackord@kw.igs.net - revised 18 Mar 04 - Liberty Basic v4.00
' Euler and Feynman algorithm graphs

' Initialize Window
  nomainwin
  WindowWidth=460     ' pixel scale 0-450
  WindowHeight=389    ' pixel scale 0-360
  UpperLeftX=50: UpperLeftY=100
  open "Euler and Feynman Graphs" for graphics_nsb as #1
  #1 "trapclose [quit]"
  #1 "cls ; down ; color black ; place 38 12 ; box 438 312"
  #1 "place 35 332": #1 "\0": #1 "place 435 332": #1 "\1"
  #1 "place 238 344": #1 "\T"
  #1 "place 26 318": #1 "\0": #1 "place 26 18": #1 "\2"
  #1 "place 6 170": #1 "\Y"
  k=8: m=2: dt=.2
  t=0: y=0: v=2.8: a=0-k*y/m                           ' Euler Algorithm
  #1 "color blue ; place 220 180"
  #1 "\Euler Algorithm"
  #1 "place 38 312"
  for i=1 to 5
    t=t+dt: y=y+v*dt: v=v+a*dt: a=0-k*y/m
    #1 "goto "; 38+int(400*t); " "; 312-int(150*y)
  next i
  t=0: y=0: v=2.8: a=0-k*y/m                           ' Feynman Algorithm
  #1 "color red ; place 220 225"
  #1 "\Feynman Algorithm"
  #1 "place 38 312"
  v=v+a*dt/2
  for i=1 to 5
    t=t+dt: y=y+v*dt: a=0-k*y/m: v=v+a*dt
    #1 "goto "; 38+int(400*t); " "; 312-int(150*y)
  next i
  t=0:y=0: dt=.005                                     ' Analytic Solution
  #1 "color black ; place 220 270"
  #1 "\Analytic Solution"
  #1 "place 38 312"
  for i=1 to 200
    t=t+dt: y=1.4*sin(2*t)
    #1 "goto "; 38+int(400*t); " "; 312-int(150*y)
  next i
  wait

[quit]
  close #1
end