c
c Code to visualize the sinc function in time and frequency domains
c	for MAST-811 Time Series Analysis
c
c Sept.-28, 2010 amue
c
	real pi,x,y,t,dt,arg,y2,ymin2
	pi = 4.*atan2(1.,1.)
c
c Record Length (Data Window or Filter Length)
c
	T = 10.
c
c Time step in hours (if you wish)
c
	dt = 0.25
c
c number of data points
c
	N = 800
c
c find maximum of the first side-lobe
c
	ymax = -999.
	ymax2 = -999.
c
c Run over all data points to get sinc function
c
	do 1 i=1,N
	   time = float(i-n/2)*dt
	   frequency = time*0.01
	   arg = pi/T*time
c
c Special Case at t=0 or f=0
c
	   if (arg .ne.0) then
	   	y = T*sin(arg)/arg
	   else
		y = T
	   end if
	   arg2 = pi/T/2.*time
	   if (arg2 .ne.0) then
	   	y2 = T/2*(sin(arg2)/arg2)*(sin(arg2)/arg2)
	   else
		y2 = T/2
	   end if
c	   write(7,*)time,sqrt(y*y),sqrt(y2*y2),frequency
	   write(7,*)time,y,y2,frequency
	   if (sqrt(y*y).gt.ymax .and. time.lt.-T)  ymax = sqrt(y*y)
	   if (sqrt(y2*y2).gt.ymax2 .and. time.lt.-T*2)  ymax2 = sqrt(y2*y2)
1	continue
c
c Height of first side-lobe in db (decibels)
c
	db = 20*log10(ymax/T)
	db2 = 20*log10(ymax2/(T/2))
	write(6,*)'Amplitude a of first lobe: ',ymax, '  20*log10(a/a0): ', db, ' decibel'
	write(6,*)'Amplitude a of first lobe: ',ymax2, ' 20*log10(a/a0): ', db2, ' decibel'
	stop
	end