1.4.1.0 measures.frequency

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measures.frequency - Function

1.4.1 define a 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 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 LGROUP CMB.
Note that additional ones may become available. Check in CASA with:

print "\t----\t frequency Ex 1 \t----"
print me.listcodes(me.frequency())
#{’normal’: [’REST’, ’LSRK’, ’LSRD’, ’BARY’, ’GEO’, ’TOPO’,
# ’GALACTO’, ’LGROUP’, ’CMB’], ’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 energy (h.nu): 8.27134e-9ueV
value as momentum: 4.42044e-42kg.m

Arguments


Inputs
rf	reference code
	allowed:	string
	Default:	LSRK
v0	frequency/wavelength/…
	allowed:	any
	Default:	variant
off	optional offset frequency measure
	allowed:	record
	Default:

Returns
record

Example

print "\t----\t frequency Ex 2 \t----"
print me.frequency(’lsrk’,’5GHz’)
#{’m0’: {’value’: 5000000000.0, ’unit’: ’Hz’},
# ’refer’: ’LSRK’,
# ’type’: ’frequency’}
print me.frequency(’lsrk’,’21cm’)
#{’m0’: {’value’: 1427583133.3333333, ’unit’: ’Hz’},
# ’refer’: ’LSRK’,
# ’type’: ’frequency’}

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