function Cv2Grid, ZP, nX, nY, dist=Dist, zflag=Zflag, noflag=NoFlag, xp=XP, yp=YP, position=position
;XB,YB,XE,YE

@compile_opt.pro			; On error, return to caller

;+
; NAME:
;	Cv2Grid
; PURPOSE:
;	Generate function values in a regular grid of NX by NY points.
;	The input function values are specified on a set random points XP,YP
;	with function values ZP, or as a 2-D array ZP
; CALLING SEQUENCE:
;	Z = Cv2Grid (ZP, nX,nY, dist=Dist, xp=XP, yp=YP, pos=pos, zflag=Zflag, noflag=NoFlag)
;	Z = Cv2Grid (ZP, nX,nY, dist=Dist, zflag=Zflag, noflag=NoFlag)
; INPUTS:
;	ZP		array[*] or array[*,*]; type:float
;				if array[*]	 : function values for a 'random' set of data points
;				if array[*,*]: any 2-dim array to be rebinned
;	nX		scalar; type: integer
;	nY		scalar: type: integer
;				size of regular output array
; OPTIONAL INPUTS:
;	dist=Dist
;			scalar; type: float
;				data points closer than abs(Dist) grid
;					spacings from an output grid point are included
;					in the averaging
;	xp=XP	array[*]; type: float
;	yp=YP	array[*]; type: float
;				X/Y-coordinates of points in the random set in user-specified units
;	position=[XB,YB,XE,YE]
;			array[4]; type: float
;				XB,YB)		X/Y-coordinates of grid point (0,0) in user units
;				XE,YE		X/Y-coordinates of grid point (nX-1,nY-1) in user units
;	zflag=ZFlag
;			scalar; type: float; default: !values.f_nan
;				value used to identify invalid fnc-values in in- and output Z
;	/noflag		if set, no fnc-values are flagged as 'bad'
; OUTPUTS:
;	Z		array[nX,nY]; type: float
;				grid function values.
;				If no function value was calculated for a particular grid point
;				the value Zflag is returned
; RESTRICTIONS:
;	The user units for XB,XE,YB,YE should be the same as for XP and YP
; PROCEDURE:
; >	If both keywords xp and yp are present, then zp is assumed to be 1-dim
;	array of 'random' points. Otherwise zp is assumed to be a 2-dim array.
; >	The output grid defines a regular grid of nX by nY squares.
; >	The function values Z are calculated by averaging over points ZP
;	inside a grid square.
; MODIFICATION HISTORY:
;	JAN-1995, Paul Hick (UCSD); based on Fortran routine CONSTRUCT_GRID
;-

if not keyword_set(XP) and not keyword_set(YP) then begin
	a = size(Z)
	if a[0] ne 2 then message, 'input must be a 2-D array
	mX = a[1]  &  mY = a[2]

; Intercept special case: no averaging, no flagging

	if nX eq mX and nY eq mY and Dist eq 1. and NoFlag then	$
		 return, Z								$

	else										$
		return, Cv2Grid(Z, nX,nY, dist=Dist,	$
			xp	= indgen(mX)#replicate(1,mY),	$
			yp	= replicate(1,mX)#indgen(mY),	$
			pos = [0,0,mX-1,mY-1], zflag=ZFlag, noflag=NoFlag)

endif

Noflag = keyword_set(NoFlag)
if n_elements(ZFlag) eq 0 then ZFlag = !values.f_nan else ZFlag = float(ZFlag[0])

dX = (position[2]-position[0])/(nX-1.0)	; Grid spacings in user units
dY = (position[3]-position[1])/(nY-1.0)

Dist = Dist > 0.
xDis = abs(dX*Dist)
yDis = abs(dY*Dist)

Z = replicate(ZFlag,nX,nY)				; Clear arrays associated with new grid

for i=0,nX-1 do begin
	X = XB+i*dX
	for j=0,nY-1 do begin
		Y = YB+j*dY
		n = where( (NoFlag or ZP ne ZFlag) and abs(XP-X) lt xDis and abs(YP-Y) lt yDis )
		if n[0] ne -1 then Z[i,j] = total(ZP[n])/n_elements(n)
	endfor
endfor

return, Z  &  end