NAME:
	rcgfit

 PURPOSE:
	Fit a radial gaussian function to the input data (no linear term).

 DESCRIPTION:
 	Fit the equation y=f(r) where:

 		F(r) = A0*EXP(-z^2/2) + A2 + A3*r^2
 			and
		z=r/A2

	A0 = height of exp, A1 = sigma (the width).
	A2 = constant term, A3 = quadratic term.
 	The parameters A0, A1, A2 are estimated and then CURVEFIT is 
	called.  The gaussian is assumed to be centered at r=0.

 CATEGORY:
	Function fitting

 CALLING SEQUENCE:
	Result = RCGAUSSFIT(R, Y [, A])

 INPUTS:
	R:	The independent variable.  R must be a vector.
	Y:	The dependent variable.  Y must have the same number of points
		as R.

 OUTPUTS:
	The fitted function is returned.

 OPTIONAL OUTPUT PARAMETERS:
	A:	The coefficients of the fit.  A is a three-element vector as 
		described under PURPOSE.

 COMMON BLOCKS:
	None.

 SIDE EFFECTS:
	None.

 RESTRICTIONS:

 PROCEDURE:
	The initial guess of the intensity is the value of the point 
	with the smallest r value.  The first point that drops below
	half of the first is the guess at the width.

 MODIFICATION HISTORY:
	DMS, RSI, Dec, 1983.
	Rewritten to change initial guess, MWB, Lowell Obs., Dec. 1992.
	Rewritten to remove background function, MWB, Lowell Obs., Jan. 1993.