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Name

tabsmooth - smooth columns of a table (Hanning, Savitzky-Golay)

Synopsis

tabsmooth [parameter=value]

Description

Quick and dirty program to smooth the column(s) of a table without paying attention to the X coordinate (meaning: a constant step size is assumed).

The filter= option is used to select the filter, for example a Hanning and a Savitzky-Golay filter (and some derivates) can be selected. A pass-through is also allowed.

Parameters

The following parameters are recognized in any order if the keyword is also given:
in=
Input file name [???]
xcol=
Column(s) to use. Although multiple columns can be used, only those columns are output to stdout. [1]
filter=
Filter option. The way the options are set will likely change, this is work in progress. 
   -1 passthrough, the column is not modified
   0  hanning (1,2,1)/4
   1  SK2 5pt smooth
   2  SK2 1st derivative with h=1
   3  SK2 2nd derivative with h=1
   4  SK4 7pt smooth
   5  SK4 1st derivative
The smoothing versions are normalized to conserve "flux". Default: 0
smooth=
Manually set the smoothing array. By default, the filter= is used to set the smoothing array. Be sure to enter an odd number of array elements, for example a normalized Hanning would be smooth=0.25,0.5,0.25. Default: not provided.
tcol=
Optional column designating the independant variable. Currently the actual value is ignored, but this column will be output before the smoothed column(s). Default: not used.

Examples

Here we draw 100000 random values from a normal distribution (mean 0, dispersion 1) and smooth them with various filters: 
tabgen - 100000 1 2 123| tabsmooth - 1 -1 | tabstat - | grep disp
1.0022
tabgen - 100000 1 2 123| tabsmooth - 1  0 | tabstat - | grep disp
0.6128
tabgen - 100000 1 2 123| tabsmooth - 1  1 | tabstat - | grep disp
0.6973
tabgen - 100000 1 2 123| tabsmooth - 1  4 | tabstat - | grep disp
0.7537

Caveats

Near the edge the smoothing array is cut off, thus there is some loss of flux. Otherwise in general the smoothing filter is normalized and should conserve flux.

See Also

tabmath(1NEMO) , tabtrend(1NEMO) , tabrows(1NEMO) , tabcols(1NEMO) , table(5NEMO)

Author

Peter Teuben

History


20-dec-2010    V0.1 Created    PJT
13-oct-2014    documented smooth=
28-sep-2023    V0.5 added filter=    PJT
29-sep-2023    V0.6 converted to table V2    PJT
29-nov-2023    V0.7 added tcol=    PJT

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