NAME:
	rgfit

 PURPOSE:
	Fit a radial gaussian function and 2nd order polynominal to the input data.

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

 		F(r) = A0*EXP(-z^2/2) + A2 + A3*r + A4*r^2
 			and
		z=r/A2

	A0 = height of exp, A1 = sigma (the width).
	A2 = constant term, A3 = linear term, A4 = 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 = GAUSSFIT(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 five-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.

	If the (MAX-AVG) of Y is larger than (AVG-MIN) then it is assumed
	that the line is an emission line, otherwise it is assumed there
	is an absorbtion line.  The estimated center is the MAX or MIN
	element.  The height is (MAX-AVG) or (AVG-MIN) respectively.
	The width is found by searching out from the extrema until
	a point is found less than the 1/e value.

 MODIFICATION HISTORY:
	DMS, RSI, Dec, 1983.
	Rewritten to change initial guess, MWB, Lowell Obs., Dec. 1992.
	93/05/11, put in failsafe on gaussian width guess, MWB, Lowell Obs.