Fit 3-parameter family of functions to 1-D data
							            2000-02-23
I: GUI
II: Usage
III: Features


                   I: Brief description of GUI

                            First Row

FIT: fit the defined MODEL to the data over specified XRANGE
VIEW: plot data and models
--> SHOW: display in X-windows
--> Hardcopy: make postscript plot
--> Set Default: change plot attributes via keyboard
    (type Q to return to widget control)
XRANGE: change range over which data are fit
--> Cursor: interactively select the range
--> Keyboard: enter Xmin, Xmax via keyboard
--> Guess: take a guess based on thawed positions
--> RESET: reset range to default value
MODEL: control model components and parameters
--> Freeze All: Freeze all parameters
--> Thaw All: Thaw all parameters
--> Freeze Unimportant: Freeze all parameters outside chosen XRANGE
--> Delete Component: Delete a model component (try not to do this!)
--> ADD Component: add a component to the models (use wisely!)
CONTINUUM: define the continuum
--> (sub XRANGE): remove lines from chosen sub range
--> (full XRANGE): remove lines over entire spectrum
--> Piecewise: interactively set a piecewise linear continuum
--> ACCEPT: unless *accepted*, newly defined continuum will not take effect
--> RESET: rest continuum to the original values
WIDTH: parameter for CONTINUUM, approximate line width [pixels]
THRESHOLD: parameter for CONTINUUM, threshold to flag a feature as
    significantly above background [Gaussian $\sigma$]
QUIT: quit program

                           Second Row

Status messages.

                            Third Row

HELP: display this document
RENORM: renormalize non-frozen fluxes to match the summed spectrum
UNDO FIT: replace fit parameters and errors with pre-fit values
SAVE: replace original values of fit parameters/errors with current values
Reset Original: EMERGENCY RESET to original values
DUMP: dump the current state to an IDL save file.  this state may be
    recovered using FITLINES_UNDUMP.PRO
ERRORS: compute projection errors
dCHI: change in chisq to use to find projection error bounds
Fit Algorithm: LevMarq and IDL's native CURVEFIT are implemented
    (But CURVEFIT does not handle frozen parameters)

                           Fourth Row

Left column: Entry fields to edit parameter values of specified component.
-- Type index in topmost field to access the parameters for that component.
-- Position      is echoed and may be changed in the second field from the top.
-- Width         is echoed and may be changed in the third field from the top.
-- Flux       	 is echoed and may be changed in the fourth field from the top.
-- Function type is echoed and may be changed in the bottommost field.
	Valid function types (if FUNCS=X3MODEL) are
	Gaussian ("G" "g" "gauss" "Gaussian" etc.)
	Lorentzian ("L" "l" "lor" "lorentz" etc.)
	Beta-profile ("Beta=<value>" "b=<value>" "beta <value>"
		"beta:<value>" "beta<tab><value>" etc.)
	Asymmetric Beta-profile ("slant=<angle>,<beta>" "s:<a> <b>", etc.)
	Broken Power-law ("pl=<break>")
		-- in this case, "Position" and "Width" actually refer to
		the two power-law indices

Right column: list of model parameters with checkboxes to freeze or thaw
    particular parameters.

                            Fifth Row

TIES: set up constraints on parameters
--> Positions: force positions to be within dPOS
--> Widths: force widths to be within dWDT
--> Fluxes: force fluxes to be within dFLX*YSIGMA
DELETE: delete parameter constraints
--> Selected: delete constraints selected with mouse clicks
--> Clear All: delete them all, god will know her own.
EDIT: edit selected constraint
ADD: add a new constraint

                            Sixth Row

dPOS: leeway for position constraints, held to +- dPOS
dWDT: leeway for width constraints, held to +- dWDT
dFLX: leeway for flux constraints, held to +- dFLX*YSIGMA

List of all existing ties.



                   II. How to use this program

     http://hea-www.harvard.edu/~kashyap/scar.html#FITLINES



                          III. Features

TBW.