----- file created by makedoc on: Tue Feb 11 14:15:25 2003
----- Documentation for /scisoft/IDL/scisoft/xaid/src//bftr.pro -----

 NAME:
	BFTR

 PURPOSE:
	This procedure calculates the Back Fourier Transform of a set

 CATEGORY:
	XAID xafs data analysis package. 

 CALLING SEQUENCE:

	BFTR, fourier, backftr

 INPUTS:
	fourier:  a 4 col set with r,modulus,real and imaginary part
		of a Fourier Transform of an Exafs spectum, as produced
		by FTR or FASTFTR procedures
	backftr: a 4-column set with the  conjugated variable k (col 0), 
	the real part (col 1), the modulus (col 2) and phase (col 3)
	of the Back Fourier Transform

 OPTIONAL INPUTS:
	
 KEYWORD PARAMETERS:
	KRANGE=[kmin,kmax] : range of the conjugated variable k for 
		the anti-transformation (default = [2.,15.])
	NPOINT= number of points of the conjugated variable for the output
		(default = 512)

 OUTPUTS:
	This procedure returns a 4-columns array (backftr) with
	the conjugated variable (k) in column 0, the real part of the
	BFT in col 1, the modulus in col 2 and the phase in col 3.

 OPTIONAL OUTPUTS:

 COMMON BLOCKS:

 SIDE EFFECTS:
	None

 RESTRICTIONS:
	None

 PROCEDURE:
	Reciprocal to FTR

 EXAMPLE:
		BFTR,fourier,backftr,krange=[2,12]

 MODIFICATION HISTORY:
 	Written by:	Manuel Sanchez del Rio. ESRF
	March, 1993	

