wiki:ShFilter
Last modified 10 years ago Last modified on 06/28/2012 04:10:00 PM

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filter traces

command: FILTER <kind> <trc-list> [<lo-wdw> <hi-wdw>] [<att>]

Filters traces with filters read in previously by a FILI command (kinds 'F' and 'R') ar attenuates traces (kind 'A'). All filters of the specified kind (<kind>) in memory are applied sequentially to the traces. If no time window (<lo-wdw>, <hi-wdw>) is specified, the whole traces are filtered. No respect is payed to a globally set time window (see STW). If <kind> 'A' is selected, the desired attenuation must be passed in parameter <att> (t* in sec).

The result of filtering is displayed in new traces. The input traces remain unchanged.

parameters

  • <kind> parameter type: char
    Kind of filter. Valid values are
    • 'F' - applies FFT filter, previously read in by a "FILI F <file>" command
    • 'T' - applies digital filter, previously read in by a "FILI T <file>" command
    • 'R' - applies recursive filter, previously read in by a "FILI R <file>" command
    • 'A' - attenuation with t* = <att> sec
    • 'H' - computes Hilbert transformation
    • 'M' - computes minimum delay wavelet
    • 'P' - (undocumented)
  • <trc-list> parameter type: trace list
    Input traces for filtering. These trace remain unchanged. If no time window is entered, all traces are filtered.
  • <lo-wdw>, <hi-wdw> parameter type: real
    Time window on all traces. The filtering of the input traces is restricted to this time window.
  • <att> parameter type: real
    Attenuation (t* in sec). Only valid for <kind> = 'A'.

qualifiers

  • /taper=<tapval>
    Valid only for FFT and digital filters. Applies a cosine taper to filtered trace in frequency domain. <tapval> ranges from 0.0 to 1.0. Default value is 1.0. The taper is started at sample <tapval>*N if N is the length of the trace in frequency domain. A value of 1.0 and greater means that no taper is applied.
  • /demean
    (undocumented)
  • /lpc
    (undocumented)

example

filter F ALL
filters all traces with the previous read filter in full length
filter F 1-3 10 110
filters traces 1-3 within time window 10..110