.help fitfunction Jul84 noao.twodspec.multispec
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NAME
fitfunction -- Fit a function to the spectra parameter values
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USAGE
fitfunction image
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PARAMETERS
.ls image
Image in which the parameter values are to be fitted.
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.ls parameter = "x0"
Parameter to be fit.  The legal minimum match abbreviated parameters
are x0, s0, s1, s2.
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.ls lines = "*"
Sample image lines to be used in the function fit.
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.ls spectra = "*"
Spectra for which the parameters are to be fit.
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.ls function = "interpolation spline"
Fitting function to be used.  The function is specified as a string
which may be minimum match abbreviated.  The functions currently available
are:
.ls interpolation spline
Interpolation spline of specified order.
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.ls smoothing spline
Smoothing spline of specified order and number of polynomial pieces.
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.ls spline_order = 4
Order of the fitting spline.  The order must be even.
The minimum value is 2 and maximum value is determined from the number of
sample lines in the fit.
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.ls spline_pieces = 1
The number of polynomial pieces in a smoothing spline.
The minimum value is 1 and the maximum value is determined from the number of
sample lines in the fit.
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DESCRIPTION
A function is fit to the parameter values previously determined at the sample
lines for each spectrum.  The function coefficients are stored in the
database and the fitted values replace the original values at all the sample
lines (not just the sample lines used in the fit).  The type of function,
the parameter to be fitted, the sample lines used in the fit, and the
spectra to be fitted are all selected by the user.  The function is
extrapolated to cover all image lines.

The values of the function fit at arbitrary image lines may be listed
with \fBmslist\fR.
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EXAMPLES
The extraction of the spectra requires that a fitting function be
determined for the spectra positions.  This is done by:

	cl> fitfunction image

To smooth the parameter "s0" in model \fIgauss5\fR with a cubic spline
and leave out a bad point at sample line 7:

.nf
	cl> fitfunction image parmeter=s0 function=smooth \
	>>> lines="1-6,8-"
.fi
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SEE ALSO
mslist
.endhelp
