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.