! PHYS 2P20 - 2020-21 Lab3: damped harmonic oscillator
!
! By Edward Sternin
! 2020.09.29

read damped.txt t\1 ay\3 

clear
defaults

set 
  xlabel `Time, s'
  ylabel `Acceleration, m/s<^>2'

graph t,ay

scales 0 4 4 0 0 0
clear\noreplot
replot

Pi=asin(1.0)*2.0

scalar\vary g,a,w,t0
g=9.8
w=2*Pi/0.5
t0=0.45
a=6

inquire `Initial fit to g+a*sin[w*(t-t0)]: {g a w t0} = {'//rchar(g)//` '//rchar(a)//` '//rchar(w)//` '//rchar(t0)//`} ' g a w t0

scales 0 max(t) 0 0 0 0
clear\noreplot
replot

t2=t0
i=0

loop:
  t1=t2
  t2=t1+4*Pi/w
  if (t2>max(t)) then goto done
  tt=t[iclose(t,t1):iclose(t,t2)]
  aa=ay[iclose(t,t1):iclose(t,t2)]
  fit\e2 aa=g+a*sin(w*(tt-t0))
  set color -(mod(i,17)+2)
  graph\overlay tt,g+a*sin(w*(tt-t0))
  i=i+1
  tf[i]=0.5*(t1+t2)
  f[i]=w
  df[i]=fit$e2[3]
goto loop

done:
list tf,f,df

terminal

clear
defaults
set
  xlabel `Time, s'
  ylabel `<omega>, rad/s'
  pchar -17
  %xloweraxis 15
  %yloweraxis 12

graph tf,f,df