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measures.frequency - Function



Package general
Module measures
Tool measures


define a frequency measure


Synopsis
frequency(rf, v0, off)


Arguments

rf in reference code
    Allowed: coded string
v0 in frequency/wavelength/...
    Allowed: quantity
    Default: 0Hz
off in optional offset
    Allowed: frequency measure
    Default: F


Returns
frequency measure


Description
frequency defines a frequency measure from the CLI. It has to specify a reference code, frequency quantity value (see introduction for the action on a scalar quantity with either a vector or scalar value, and when a vector of quantities is given), and optionally it can specify an offset, which in itself has to be a frequency. Allowable reference codes are: REST LSRK LSRD BARY GEO TOPO GALACTO.
Note that additional ones may become available. Check in Glish with:
- dm.listcodes(dm.frequency())
[normal=REST LSRK LSRD BARY GEO TOPO GALACTO, extra=]
The frequency quantity values should be in one of the recognised units (examples all give same frequency):
  • value with time units: a period (0.5s)
  • value as frequency: 2Hz
  • value in angular frequency: 720deg/s
  • value as length: 149896km
  • value as wave number: 4.19169e-8m-1
  • value as enery (h.nu): 8.27134e-9ueV
  • value as momentum: 4.42044e-42kg.m



Example
- dm.frequency('lsrk', '5GHz')
[type=frequency, refer=lsrk, m0=[value=5e+09, unit=Hz]] 
- dm.frequency('lsrk', '21cm')
[type=frequency, refer=lsrk, m0=[value=1.42758e+09, unit=Hz]]





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