4.1.1.0 atmosphere.getChanNum

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atmosphere.getChanNum - Function

4.1.1 Get the grid position for a given frequency in the specified spectral window.

Description

Return the channel number for given frequency in the specified spectral window relative to the reference channel number.

Arguments


Inputs
freq	GHz	Frequency
		allowed:	doubleGHz
		Default:
spwid		Int standing for spectral window id (0-based). The value must be >= 0.
		allowed:	int
		Default:	0

Returns
double

Example

# List current spectral window setting of SPW0
at.getRefFreq()[’value’][0], at.getRefFreq()[’unit’]
# (90.0, ’GHz’)
print at.getChanSep()[’value’][0], at.getChanSep()[’unit’]
# 10.0 MHz
at.getRefChan()
# 32

# Get grid positions
at.getChanNum(qa.quantity(90., ’GHz’))
# 0.0

at.getChanNum(qa.quantity(90., ’GHz’), 0)
# 0.0

at.getChanNum(qa.quantity(90.08, ’GHz’), 0)
# 8.0

at.getChanNum(qa.quantity(89.985, ’GHz’), 0)
# -1.5

at.getChanNum(qa.quantity(89.98,’GHz’), 0)
# -2.0

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