function boxave, array, xsize, ysize ;+ ; NAME: ; BOXAVE ; PURPOSE: ; Box-average a 1 or 2 dimensional array. ; EXPLANATION: ; This procedure differs from the intrinsic REBIN function in the follow ; 2 ways: ; ; (1) the box size parameter is specified rather than the output ; array size ; (2) for INTEGER arrays, BOXAVE computes intermediate steps using REAL*4 ; (or REAL*8 for 64bit integers) arithmetic. This is ; considerably slower than REBIN but avoids integer truncation ; ; CALLING SEQUENCE: ; result = BOXAVE( Array, Xsize,[ Ysize ] ) ; ; INPUTS: ; ARRAY - Two dimensional input Array to be box-averaged. Array may be ; one or 2 dimensions and of any type except character. ; ; OPTIONAL INPUTS: ; XSIZE - Size of box in the X direction, over which the array is to ; be averaged. If omitted, program will prompt for this ; parameter. ; YSIZE - For 2 dimensional arrays, the box size in the Y direction. ; If omitted, then the box size in the X and Y directions are ; assumed to be equal ; ; OUTPUT: ; RESULT - Output array after box averaging. If the input array has ; dimensions XDIM by YDIM, then RESULT has dimensions ; XDIM/NBOX by YDIM/NBOX. The type of RESULT is the same as ; the input array. However, the averaging is always computed ; using REAL arithmetic, so that the calculation should be exact. ; If the box size did not exactly divide the input array, then ; then not all of the input array will be boxaveraged. ; ; PROCEDURE: ; BOXAVE boxaverages all points simultaneously using vector subscripting ; ; NOTES: ; If im_int is a 512 x 512 integer (16 bit) array, then the two statements ; ; IDL> im = fix(round(rebin(float(im_int), 128, 128))) ; IDL> im = boxave( im_int,4) ; ; give equivalent results. The use of REBIN is faster, but BOXAVE is ; is less demanding on virtual memory, since one does not need to make ; a floating point copy of the entire array. ; ; REVISION HISTORY: ; Written, W. Landsman, October 1986 ; Call REBIN for REAL*4 and REAL*8 input arrays, W. Landsman Jan, 1992 ; Removed /NOZERO in output array definition W. Landsman 1995 ; Fixed occasional integer overflow problem W. Landsman Sep. 1995 ; Allow unsigned data types W. Landsman Jan. 2000 ; Assume since V5.4, Allow 64bit integers W. Landsman Apr 2006 ;- On_error,2 compile_opt idl2 if N_params() EQ 0 then \$ message,'Syntax - out = BOXAVE( array, xsize, [ysize ])',/NoName s = size(array) if ( s[0] NE 1 ) && ( s[0] NE 2 ) then \$ message,'Input array (first parameter) must be 1 or 2 dimensional' if N_elements(xsize) EQ 0 then read,'BOXAVE: Enter box size: ',xsize if N_elements(ysize) EQ 0 then ysize = xsize s = size(array) ninx = s[1] noutx = ninx/xsize type = s[ s[0] + 1] integer = (type LT 4) || (type GE 12) if s[0] EQ 1 then begin ; 1 dimension? if integer then begin if xsize LT 2 then return, array counter = lindgen(noutx)*xsize output = array[counter] for i=1,xsize-1 do output = output + array[counter + i] if type GE 14 then nboxsq = double(xsize) else nboxsq = float(xsize) endif else return, rebin( array, noutx) ;Use REBIN if not integer endif else begin ; 2 dimensions niny = s[2] nouty = niny/ysize if integer then begin ;Byte, Integer, or Long if type GE 14 then begin nboxsq = double( xsize*ysize ) output = dblarr( noutx, nouty) ;Create output array endif else begin nboxsq = float( xsize*ysize ) output = fltarr( noutx, nouty) ;Create output array endelse counter = lindgen( noutx*nouty ) counter = xsize*(counter mod noutx) + \$ (ysize*ninx)*long((counter/noutx)) for i = 0L,xsize-1 do \$ for j = 0L,ysize-1 do \$ output = output + array[counter + (i + j*ninx)] endif else \$ return, rebin( array, noutx, nouty) ;Use REBIN if not integer endelse case type of 12: return, uint(round( output/nboxsq )) ;Unsigned Integer 13: return, ulong( round(output/nboxsq)) ;Unsigned Long 14: return, round(output/nboxsq, /L64) ;64bit integer 15: return, ulong64(round(output/nboxsq,/L64)) ;Unsigned 64bit 2: return, fix( round( output/ nboxsq )) ;Integer 3: return, round( output / nboxsq ) ;Long 1: return, byte( round( output/nboxsq) ) ;Byte endcase end