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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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