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sd.scantable.auto_sinusoid_baseline  Function
5.1.2 Perform automatic line finding and baseline subtraction using sinusoidal
function
Description
Return a scan which has been baselined (all rows) with sinusoidal functions.
Fit will be done with ’sigmaclipping’.
Spectral lines are detected first using linefinder and masked out to avoid them affecting the baseline solution.
If applyfft is set to True, the function performs Fourier analysis to select wave numbers for sinusoidal fitting. Currently, ’fft’ is only available to be used for the analysis. You can specify threshold for selection of wave number using fftthresh parameter. Both float and string is acceptable. Given a float value, the unit is set to sigma. For string values, allowed formats include:
 any decimal number plus ’sigma’ (e.g. ’3sigma’)
 ’top’ plus any decimal number (e.g. ’top10’)
In addition, you can add or reject specific wave numbers from the fit using addwn and rejwn, respectively. You can specify wave numbers as an integer, string, or list of them. For string specification, syntax for those parameters are as follows:
 ’ab’ (= a, a+1, a+2, ..., b1, b)
 ’<a’ (= 0, 1, ..., a2, a1)
 ’>a’ (= a+1, a+2, ... up to maximum wave number corresponding to the Nyquist frequency)
You can append ’=’ after inequality sign. When both addwn and rejwn are set, rejwn will take priority of addwn.
The edge argument is an optional number of channel to drop at the edge of spectrum. If only one value is specified, the same number will be dropped from both sides of the spectrum. Default is to keep all channels. Nested tuples represent individual edge selection for different IFs (a number of spectral channels can be different).
The threshold and chan_avg_limit arguments are linefinder options. The former is the threshold used by line finder. It is better to keep it large as only strong lines affect the baseline solution. The later is a maximum number of consequtive spectral channels to average during the search of weak and broad lines. The default is no averaging (and no search for weak lines). If such lines can affect the fitted baseline (e.g. a high order polynomial is fitted), increase this parameter (usually values up to 8 are reasonable). Most users of this method should find the default value sufficient. See linefinder for more details on these options.
Note: The bestfit parameter values output in logger and/or blfile are now based on specunit of ’channel’.
Arguments
Inputs 
 
insitu 
 If False a new scantable is returned  
 allowed:  bool 

 Default:  None (use default value) 

mask 
 An optional mask retreived from scantable
 
 allowed:  bool array 

 Default:  None (no mask) 

applyfft 
 Perform Fourier analysis to find appropriate sinusoidal
component
 
 allowed:  bool  
 Default:  True 

fftmethod 
 Method to find sinusoidal component (currently only ’fft’
is available)
 
 allowed:  string 

 Default:  ’fft’  
fftthresh 
 Threshod to select wave number in Fourier analysis
 
 allowed:  float, string 

 Default:  3.0  
addwn 
 Additional wave numbers to be used for fitting
 
 allowed:  integer, string, any array 

 Default:  [] 

rejwn 
 Waver numbers not to be used for fitting
 
 allowed:  integer, string, any array 

 Default:  [] 

clipthresh 
 Clipping threshold in unit of sigma
 
 allowed:  float  
 Default:  3.0 

clipniter 
 Maximum number of iteration of clipping
 
 allowed:  integer 

 Default:  0 

edge 
 An optional number of channel to drop at the edge of
spectrum
 
 allowed:  integer, integer array 

 Default:  (0,0) 

threshold 
 The threshold used by line finder
 
 allowed:  float 

 Default:  3 

chan_avg_limit 
 A maximum number of consequtive spectral channels to
average during the search
 
 allowed:  int 

 Default:  1 

plot 
 Plot the fit and the residual (currently unavailable)
 
 allowed:  bool 

 Default:  False 

getresidual 
 If False, return bestfit value instead of residual
 
 allowed:  bool 

 Default:  True 

showprogress 
 Show progress status for large data
 
 allowed:  bool 

 Default:  True 

minnrow 
 Minimum number of spectra to show progress status
 
 allowed:  integer 

 Default:  1000 

outlog 
 Output the coefficients of the bestfit function to logger
 
 allowed:  bool 

 Default:  False 

blfile 
 Name of text file in which the bestfit parameter values
to be written
 
 allowed:  string 

 Default:  ” 

scantable
Example
scan2 = scan.auto_sinusoid_baseline(addwn=’<=10’, insitu=False)
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This code is available under the terms of the GNU General Public Lincense
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