----- file created by makedoc on: Tue Feb 11 14:15:23 2003
----- Documentation for /scisoft/IDL/scisoft/xaid/src//fastftr.pro -----

 NAME:
	FASTFTR

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

 CATEGORY:
	XAID xafs data analysis package. 

 CALLING SEQUENCE:

	FASTFTR, 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 the fft calculation (default = 4096)
	KSTEP = step of the k variable for the interpolation

 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 FFT IDL's function

 EXAMPLE:
		FASTFTR,setin,fourier

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