recursive_df.pro

IDL语言编写的用于天文自适应光学仿真的软件CAOS V6.0的第一部分。

; $Id: recursive_df.pro,v 1.2 2002/03/14 11:49:11 riccardi Exp $

function recursive_df, x, numd, dend

n = n_elements(x)
nd= n_elements(dend)
nn= n_elements(numd)

if dend[0] eq 0 then message,'the digital filter must have den_d[0] ne 0'

y = replicate(0B*x[0], n)

numr = rotate(numd,2)
denr = rotate(dend[1:nd-1],2)
if dend[0] ne 1.0 then begin
    numr = numr/dend[0]
    denr = denr/dend[0]
endif
;for i=nf-1,n-1 do y[i]=total(numr*x[i-nf+1:i])-total(denr*y[i-nf+1:i-1])

y[0] = numr[nn-1]*x[0]
for i=1,n-1 do $ ; compute filtered signal recursively
  y[i]=total(numr[nn-1-i>0:*]*x[i-nn+1>0:i]) $
  -total(denr[nd-1-i>0:*]*y[i-nd+1>0:i-1])

return, y
end