;  $Id: pdecay.pro,v 1.1 2004/04/11 17:14:00 brandenb Exp $
;
;  procedure for calculating the decay exponent
;
@param
default,dt0,0
default,t1,0
default,t2,1e9
default,tau,21.
;
t0=tt(0)+dt0
d0=deriv(alog10(tt-t0),alog10(urms^2))
d1=deriv(alog10(tt-t0),smooth(alog10(urms^2),200))
d2=deriv(alog10(tt-t0),smooth(alog10(urms^2),500))
;
!p.multi=[0,1,2]
plot_oo,tt-t0,urms^2/urms(0)^2,xr=[1,200]
oplot,tt-tt(0),1./((tt-tt(0))/tau)^1.25,col=122,li=2
;
plot,tt,d1,yr=[-2,-.5]
oplot,tt,d2,col=122
;
;  fit
;
good=where(tt gt t1 and tt lt t2)
n=mean(d2(good))
print,'t1,t2,n=',t1,t2,n
oplot,tt(good),(tt-tt+n)(good)
;
END