- Form: SPLINE source [R=r1,r2,...] [C=c1,c2...]
[W=w1,w2,...]
-
- [AVG=a] [SUB] [DIV]
- source
- is the image or spectrum SPLINE works on
- R=r1,r2,...
- replaces each column in the image 'source'
with the best spline through the knot points at rows r1,r2,...
- C=c1,c2,...
- replaces each row in the image (or uncalibrated
spectrum) 'source' with the best spline
through the knot points at columns c1,c2,...
- W=w1,w2,...
- replaces a wavelength calibrated spectrum
'source' by the best-fitting spline with knot
points at wavelengths w1,w2,...
- AVG=a
- averages a pixels or Angstroms around the knots.
- SUB
- subtracts the best fitting spline(s) from the
rows or columns, instead of replacing by the spline.
- DIV
- divides each row/column by the best fitting
spline, instead of replacing by the spline.
SPLINE is used to fit splines to images or spectra. When used with images,
it replaces each row (or column) with splines fitted with designated
columns (or rows) as knot points. When used with (wavelength calibrated)
spectra, it replaces the spectrum with the best fitting spline with
designated columns (Angstroms) as knot points.
Examples:
- SPLINE 11 W=5000,5500,6000,7000
- replaces spectrum 11 with
the best-fitting spline. Knot points are at 5000, 5500, 6000, 7000
Angstroms.
- SPLINE 11 W=5000,5500,6000,7000 AVG=40
- does the same as
example 1, but takes the average in 40 Angstrom bins around the
designated knot points. The averages are used in the spline fit.
- SPLINE 11 W=5000,5500,6000,7000 DIV
- does the same ax
example 1, but divides the spectrum by the best fitting spline
instead of replacing by the spline.
- SPLINE 11 C=20,40,100,300,500 AVG=10
- this form is used for
spectra that are not wavelength calibrated. It averages the
spectrum in 10 channel bins around columns 20, 40, ..., and replaces
the spectrum by the best fitting spline.
Example using images:
- SPLINE 11 C=20,40,100,300,500 AVG=10
- this command is the
same as example 4 above. When applied to an image, it replaces each
row in the image by the spline which best fits that row. The knot
points are taken to be averages of the image intensity in 10 channel
bins around columns 20, 40,...