NAME:
	radp
 PURPOSE: (one line)
	Extract point-wise radial ``profile'' from image data.
 DESCRIPTION:

	This routine will reorder the image into two 1-d vectors.  One vector
	is the radial distance from a point and the other vector is the
	intensity for that distance.  The image data is not modified, every
	input pixel is returned, just in a different form.

	Optionally, this program will attempt to fit a gaussian to the profile
	and will return the FWHM of the image.  You can also get the actual
	fitted coefficients and the computed functional value.  The fitting
	is done with the procedure rgfit and its associated routine
	rgauss_funct for computing the function.

 CATEGORY:
	CCD data processing
 CALLING SEQUENCE:
	radp,image,xcen,ycen,r,i,[fwhm,[coefs,[yfit]]]
 INPUTS:
	image - Input image to create profile from.
	xcen  - X-coordinate for r=0
	ycen  - Y-coordinate for r=0
 OPTIONAL INPUT PARAMETERS:
 KEYWORD PARAMETERS:
	QONLY - No linear term in fit, just constant and quadratic.
	CONLY - Guassian and constant only.
	FZWID - Freeze the full-width half max to this value.
 OUTPUTS:
	r     - the r coordinates for all input pixels.
	i     - the input image after reordering to match r vector.
 OPTIONAL OUTPUT PARAMETERS:
	fwhm  - Return value of the gaussian fit to the profile, in pixels.
	coefs - Fitted function coefficients. (See rgfit.pro)
	yfit  - Fitted values.
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
	92/11/04, Written by Marc W. Buie, Lowell Observatory