Subject: bayesian filter

pro bayesredfun,ap,sp,dtype,mf
           
;dtype=apriori distribution type, 0=constant, 1=exponential, 2=gaussian
;mf=parameter of distribution, i.e. for dtype=2, mf is the sigma
;ap is measured extinction
;sp is uncertainty of ap
;pav is the prior probability at extinctions of dmags
dmags=dindgen(10000)/1000.
pav=dblarr(10000)                   
if (dtype eq 0) then pav(*)=.1
if (dtype eq 1) then begin         
  ;read,'enter 1/e fold in magnitudes',mf
  pav=exp(-dmags/mf)
  pav=pav/total(.001*pav)
endif;
if (dtype eq 2) then begin
  ;read,'enter 1 sigma in magnitudes',mf
  pav=2./(((2*3.14)^.5)*mf)*exp(-((dmags/(1.41*mf))^2.))
endif;
!psym=-3
!linetype=0
dav=dblarr(1000)
dav=(exp(-(dmags-ap)^2./(2.*sp^2.))*pav)/(total(.001*pav*exp(-(dmags-ap)^2./(2.*
sp^2.))))

res=max(dav,kk)
ap=kk*.001 
sp=(total(.001*dav*dmags^2.)-(total(.001*dav*dmags))^2.)^.5
;the best extinction, ap,  is at the peak of the new distribution, dav
;the new uncertainty, sp, is the second moment of the new distribution, dav
; calculated by the standard formula, sigma_a=((mean(a^2)-(mean(a))^2.)^0.5
end