Документ взят из кэша поисковой машины. Адрес оригинального документа : http://hea-www.harvard.edu/PINTofALE/pro/findscale.pro Дата изменения: Tue May 27 00:20:59 2003 Дата индексирования: Tue Oct 2 00:55:07 2012 Кодировка: Поисковые слова: ngc 6992

function findscale,curve,dim,crunch=crunch,half=half,pick=pick,choice=choice,$
eps=eps,_extra=e
;+
;function findscale
; returns the lengthscale in pixels at each point on the given curve
;
;syntax
; ls=findscale(curve,dim,/crunch,/half,pick=pick,choice=choice,eps=eps)
;
;parameters
; curve [INPUT; required] regularly gridded array of function
; values to be used to compute the length scales
; * if scalar, returns 0
; * if 2D,
; -- use DIM to specify primary dimension
; -- compute lengthscales separately along each projection
; * if >2D, convert to 1D
; dim [INPUT; default=1] primary dimension in case of 2D array
; (e.g., if CURVE=CURVE(NX,NY), DIM=2 returns SCALE=SCALE(NY))
;
;keywords
; crunch [INPUT] if set, and CURVE is 2D, collapses the array along
; the secondary dimension to generate 1D curve
; half [INPUT] if set, returns the half-scale
; pick [INPUT; default=0] if 2D, specifies how to combine the
; scales computed at the different cuts
; 0: pick the smallest scale
; 1: pick the largest scale
; 2: get the average
; choice [INPUT; default=0] what algorithm to use to find the scale?
; 0: MexicanHat wavelet
; 1: use inverse of 1st derivative
; 2: radius of curvature
; 3: stepped toggle
; eps [INPUT; default=1e-7] small number
; _extra [JUNK] ignore. here only to prevent crashing program.
;
;subroutines
; WVLT_SCALE [ROOFN]
;
;history
; vinay kashyap (Apr97)
; added CHOICE option 3 (VK; Feb03)
;-

; usage
if n_elements(curve) eq 0 then begin
print,'Usage: ls=findscale(curve,dim,/crunch,/half,pick=pick,choice=choice,eps=eps)'
print,' returns length scales at each point along curve'
return,0L
endif

; save inputs
f=curve & if keyword_set(dim) then d=fix(dim) else d=1

; check dimensions
szf=size(f) & nszf=n_elements(szf)
if szf(0) eq 0 then return,[0L] ;scalar -- return 0
if szf(0) gt 2 then begin ;convert to 1D
f=[temporary(f(*))] & szf=size(f) & nszf=n_elements(szf)
endif
if szf(0) ne 2 then d=1 ;only 1 D, see?
nx=szf(1) & if szf(0) eq 1 then ny=1L else ny=szf(2)

; if primary dimension is the 2nd D, then transpose the matrix
if d eq 2 then begin
nx=szf(2) & ny=szf(1) & f=transpose(temporary(f))
endif

; catch trivial errors
if nx lt 3 then return,lonarr(NX) ;scalar masquerading as array

; collapse to 1D
if szf(0) eq 2 and keyword_set(crunch) then begin
g=reform(f(*,0))
for ix=0,nx-1 do g(ix)=total(f(ix,*))
f=g & ny=1
endif

; initialize
if not keyword_set(choice) then choice=0 ;how to make the scales
if not keyword_set(pick) then pick=0 ;how to combine scales across dimensions
scale=lonarr(nx)+nx & if pick eq 2 then scale(*)=0 ;the output
if not keyword_set(eps) then eps=1e-7 ;"epsilon"
norm=lonarr(nx) ;for PICK=2

; get length scale
scl=lonarr(nx)
for iy=0,ny-1 do begin ;{shtep through secondary dimensions
g=reform(f(*,iy)) ;la function
dg=deriv(g) ;derivative
d2g=deriv(dg) ;2nd derivative
gb=intarr(nx)+1 ;coverage function
ok=where(g lt 0.01*max(g),mok) & if mok gt 0 then gb(ok)=0
if not keyword_set(choice) then begin
scl=wvlt_scale(g,_extra=e)
endif else begin
if choice(0) eq 1 then scl=ceil(abs(g)/(abs(dg)>eps)) else $
if choice(0) eq 2 then scl=ceil((1.+dg^2)^(1.5)/(abs(d2g)>eps)) else $
if choice(0) eq 3 then scl=scl+gb else $
scl=wvlt_scale(g,_extra=e)
endelse
if choice(0) ne 3 then begin
for ix=0,nx-1 do begin ;if 2D, we gotta pick
s=scale(ix)
if g(ix) gt eps*max(f) then begin
if pick eq 0 then scale(ix)=scl(ix) < s
if pick eq 1 then scale(ix)=scl(ix) > s
if pick eq 2 then begin
scale(ix)=scl(ix) + s
norm(ix)=norm(ix)+1L
endif
endif
endfor
endif else scale=max(scl)-scl+1L
endfor ;IY=0,NY-1}
norm=norm>1 & if pick eq 2 then scale=ceil(float(scale)/float(norm))

; return the half-scale if asked
if keyword_set(half) then scale=scale/2

return,scale
end