Program:      CONREMCHEB

Purpose:      Removes continuum from channel maps by fitting a
              polynomial or a Chebychev series to the continuum channels.

Category:     ANALYSIS, COMBINATION

File:         conrem.py

Author:       M.G.R. Vogelaar

Keywords:

   INSET=     Set and subsets from which to subtract the continuum:
              
   FITSET=    Set and subsets for which to fit the continuum:
              Number of profiles with fit data must be equal to number
              of input profiles

   DEGREE=    Degree of pol. or series to be fitted:     [1]
              Maximum degree depends on the number of available
              x values in the fit.

   OUTSET=    Set and subsets for the result:
              The result depends on the value of SUBTRACT=

   FUNCTION=  Fit standard Polynomial or Chebyshev series?   P/[C]
              Default is a Chebyshev series.

   FITOUTSET= Set to write fit results only:   [skip]
              Write the fitted continuum to a set. The set is created and
              has the same size and header as the input set.
              

Description:  A polynomial or a Chebyshev series of degree NPOLY= is
              fitted to the subset selected with FITSET= for each
              grid position in the subset separately.
              This fitted polynomial can then be subtracted
              from the subsets selected with INSET= and/or can be used
              to calculate an interpolated continuum in OUTSET=.
              The program is especially useful for removing the continuum
              from a series of line maps.

Example:      <USER> CONREMCHEB
              CONREM  Version 1.0  (Jul 30 1991)
              <USER> CONREMCHEB INSET=NGC4214 3:58
              Set NGC4214 has 3 axes
              RA-NCP             from  -127 to   128
              DEC-NCP            from  -127 to   128
              FREQ-OHEL          from     1 to    63
              <USER> CONREMCHEB FITSET=NGC4214 3:16 42:58
              Set NGC4214 has 3 axes
              RA-NCP             from  -127 to   128
              DEC-NCP            from  -127 to   128
              FREQ-OHEL          from     1 to    63
              <USER> CONREMCHEB DEGREE=1
              <USER> CONREMCHEB OUTSET=NGC4214_SUB
              Set NGC4214_SUB has 3 axes
              RA-NCP             from  -127 to   128
              DEC-NCP            from  -127 to   128
              FREQ-OHEL          from     3 to    58
              <USER> CONREMCHEB FUNCTION=P
              <USER> CONREMCHEB FITOUTSET=fit4214

              <STATUS>  CONREMCHEB   +++ FINISHED +++

Updates:      Aug 28, 2013: VOG Document (based on conrem.dc1) created

Note:         This program provides functionality as in CONREM but besides a
              standard polynomial, you can also fit a Chebychev series, which
              is less sensitive to oscillations at the edges of a fit interval
              (Runge's phenomenon).

              With versions of NumPy >= 1.7.1 the fit functions accepts multiple
              profiles to fit. This makes the program (much) faster than versions
              with an older NumPy.#<