function stddevs,imgs,help=help, skymode = skymode, masks = masks,nan=nan
;+
; NAME: meds
; PURPOSE:
; 	return the standard deviations for a stack of images
; USAGE:
;      function meds,imgs,help=help, skymode = skymode, masks = masks
;
; INPUTS:
; 	imgs		a stack of images
; KEYWORDS:
; 	masks		Bad pixel mask. 0=bad, 1=good
; 	skymode		uses skymode.pro to find stddevs; disabled, not sure why
; RETURNS:
; 		an array containing the stddev for each image in the stack.
; 		That is, it computes the stddev for each image individually and
; 		returns all of those, rather than stddevning across images.
;
; HISTORY:
; 2004-10-6		split from meds.pro	MDP
;-

if n_params() lt 1 or keyword_set(help) then begin
	message,'function meds(imgs,/help,/skymode,[masks=])'
endif

sz = size(imgs)

if sz[0] lt 3 then $
	message,"First arguement to meds must be a 3D array."

mm = fltarr(sz(3))
if keyword_set(masks) then begin
    szm = size(masks)
    if total(sz(0:3)-szm(0:3)) ne 0 then begin
        message, 'images & masks do not match!', /info
        help, imgs, masks
		stop
    endif
endif


for i=0,sz(3)-1 do begin

;    if keyword_set(skymode) then $
;      mm(i) = skymode(imgs(*, *, i), /plot) $
;    else $
;      mm(i) = stddev(imgs(*,*,i))

    if keyword_set(masks) then begin
        wg = where(masks(*, *, i) eq 1, ng)
        if (ng gt 0) then mm[i] = stddev((imgs[*, *, i])[wg], /nan) $
          else message, 'no good pixels for image '+strc(i), /info
    endif else $
      mm[i] = stddev(imgs[*,*,i],/nan)

endfor

return,mm

end