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

 NAME:
	FTR

 PURPOSE:
	This procedure calculates the Fourier Transform of a set

 CATEGORY:
	XAID xafs data analysis package, 

 CALLING SEQUENCE:

	FTR, ftrin, ftrout

 INPUTS:
	ftrin:  a 2 or 3 col set with k,real(chi),imaginary(chi)
	ftrout:	a 4-column set with the  congugated variable (col 0), 
	the modulus (col 1), the real part (col 2) and imaginary 
	part (col 3) of the Fourier Transform

 OPTIONAL INPUTS:
	
 KEYWORD PARAMETERS:
	RRANGE=[rmin,rmax] : range of the congugated variable for 
		the transformation (default = [0.,6.])
	NPOINT= number of points of the congugated variable for the output
		(default = 512)

 OUTPUTS:
	This function returns a 4-columns array (ftrout) with
	the congugare variable (R) in column 0, the modulus of the
	FT in col 1, the real part in col 2 and the imaginary part in
	col 3.

 OPTIONAL OUTPUTS:

 COMMON BLOCKS:

 SIDE EFFECTS:
	None

 RESTRICTIONS:
	None

 PROCEDURE:
	Uses the standard formulae  F = Fr + i Fi   with
	Fr = [1/(2pi)] sum[ Dk ( fr cos(2kr) - fi sin(2kr) ) ]
	Fi = [1/(2pi)] sum[ Dk ( fr sin(2kr) + fi cos(2kr) ) ]

 EXAMPLE:
		FTR,setin,fourier

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