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BOXAVE

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 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

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